equationzone

Elementary Algebra

Laws of Exponents

Master the properties of exponentiation and radicals in ℝ with clear definitions and special cases. Learn about natural, fractional, and negative exponents, sign rules for powers, exponential equations, and simplifying radicals. Perfect for math students!

an={aif n=1aaan timesif nN,n2\boxed{a^n = \begin{cases} a & \text{if } n = 1 \\ \underbrace{a \cdot a \cdot \ldots \cdot a}_{n \text{ times}} & \text{if } n \in \mathbb{N}, n \geq 2 \end{cases}}

Note

The expression:

(xy)(xy)(xy)(xy)(5+3) times(xy)5+3{\underbrace{(\sqrt{xy})\cdot(\sqrt{xy})\cdot(\sqrt{xy}) \cdots (\sqrt{xy})}_{(\sqrt{5}+\sqrt{3}) \text{ times}}\neq (\sqrt{xy})^{\sqrt{5}+\sqrt{3}}}

is not defined, since (5+3){(\sqrt{5}+\sqrt{3})} is not a natural number.

Sign rule for powers with negative bases:

(b)2n=+b2n;nZ+(-b)^{2n} = +b^{2n}; \quad \forall n \in \mathbb{Z}^+

(b)2n+1=b2n+1;nZ+(-b)^{2n+1} = -b^{2n+1}; \quad \forall n \in \mathbb{Z}^+

Examples
  • 34=33334 times=813^4 = \underbrace{3 \cdot 3 \cdot 3 \cdot 3}_{4 \text{ times}} = 81
  • (12)3=1212123 times=18\left(\dfrac{1}{2}\right)^3 = \underbrace{\dfrac{1}{2} \cdot \dfrac{1}{2} \cdot \dfrac{1}{2}}_{3 \text{ times}} = \dfrac{1}{8}
  • (2)5=(2)(2)(2)(2)(2)5 times=32(-2)^5 = \underbrace{(-2) \cdot (-2) \cdot (-2) \cdot (-2) \cdot (-2)}_{5 \text{ times}} = -32
  • x3=xxx3 timesx^3 = \underbrace{x \cdot x \cdot x}_{3 \text{ times}}
  • 71=7(by definition, if n=1)7^1 = 7 \quad \text{(by definition, if } n = 1\text{)}
  • (1)6=(1)(1)(1)(1)(1)(1)6 times=1(-1)^6 = \underbrace{(-1) \cdot (-1) \cdot (-1) \cdot (-1) \cdot (-1) \cdot (-1)}_{6 \text{ times}} = 1

a0=1aR{0} \boxed{ a^0 = 1 \quad \forall a \in \mathbb{R} \setminus \{0\}}

Note:

000^0 is an indeterminate form.

Examples
  • 50=15^0 = 1
  • (7)0=1(-7)^0 = 1
  • (3.14)0=1(3.14)^0 = 1
  • (23)0=1\left(\frac{2}{3}\right)^0 = 1
  • (x2+1)0=1for any xR(x^2 + 1)^0 = 1 \quad \text{for any } x \in \mathbb{R}
  • (abc)0=1if a,b,c0(a \cdot b \cdot c)^0 = 1 \quad \text{if } a, b, c \neq 0

an=1anaR{0},nN\boxed{a^{-n} = \frac{1}{a^n} \quad \forall a \in \mathbb{R} \setminus \{0\}, n \in \mathbb{N}}

Note:

0n0^n is undefined for nNn \in \mathbb{N}.

Examples
  • 23=123=182^{-3} = \dfrac{1}{2^3} = \dfrac{1}{8}
  • 52=152=1255^{-2} = \dfrac{1}{5^2} = \dfrac{1}{25}
  • (4)3=1(4)3=164=164(-4)^{-3} = \dfrac{1}{(-4)^3} = \dfrac{1}{-64} = -\dfrac{1}{64}
  • (13)2=1(13)2=119=9\left(\dfrac{1}{3}\right)^{-2} = \dfrac{1}{\left(\dfrac{1}{3}\right)^2} = \dfrac{1}{\dfrac{1}{9}} = 9
  • x4=1x4if x0x^{-4} = \dfrac{1}{x^4} \quad \text{if } x \neq 0
  • (2a)1=12aif a0(2a)^{-1} = \dfrac{1}{2a} \quad \text{if } a \neq 0

am/n=amn=(an)mnN,n2 \boxed{ a^{m/n} = \sqrt[n]{a^m} = (\sqrt[n]{a})^m \quad \forall n \in \mathbb{N}, n \geq 2}

Note:

(+)2n+1=(+)\sqrt[2n+1]{(+)} = (+)

()2n+1=()\sqrt[2n+1]{(-)} = (-)

(+)2n=(+)\sqrt[2n]{(+)} = (+)

()2n=undefined in R\sqrt[2n]{(-)} = \text{undefined in }\mathbb{R}

Examples
  • 82/3=823=643=48^{2/3} = \sqrt[3]{8^2} = \sqrt[3]{64} = 4
  • 163/4=(164)3=23=816^{3/4} = (\sqrt[4]{16})^3 = 2^3 = 8
  • 271/3=273=327^{1/3} = \sqrt[3]{27} = 3
  • 43/2=(4)3=23=8(here  2= )4^{3/2} = (\sqrt{4})^3 = 2^3 = 8 \quad \text{(here } \sqrt[2]{\ } = \sqrt{\ }\text{)}
  • x5/2=x5=(x)5if x0x^{5/2} = \sqrt{x^5} = (\sqrt{x})^5 \quad \text{if } x \geq 0
  • (19)1/2=19=13\left(\dfrac{1}{9}\right)^{1/2} = \sqrt{\dfrac{1}{9}} = \dfrac{1}{3}
Fundamental Identity

P=an;aR,nN,PR \boxed{P = a^n; \quad a \in \mathbb{R}, n \in \mathbb{N}, P \in \mathbb{R}}

Where:

  • aa: base
  • nn: natural exponent
  • PP: power

aman=am+naR,m,nN\boxed{a^m \cdot a^n = a^{m+n} \quad a \in \mathbb{R}, m, n \in \mathbb{N}}

Examples
  • 2324=23+4=27=1282^3 \cdot 2^4 = 2^{3+4} = 2^7 = 128
  • x5x2=x5+2=x7x^5 \cdot x^2 = x^{5+2} = x^7
  • (3)2(3)6=(3)2+6=(3)8=6561(-3)^2 \cdot (-3)^6 = (-3)^{2+6} = (-3)^8 = 6561
  • a4a1=a4+1=a5a^4 \cdot a^1 = a^{4+1} = a^5
  • (12)3(12)5=(12)3+5=(12)8=1256\left(\dfrac{1}{2}\right)^3 \cdot \left(\dfrac{1}{2}\right)^5 = \left(\dfrac{1}{2}\right)^{3+5} = \left(\dfrac{1}{2}\right)^8 = \dfrac{1}{256}
  • yny7=yn+7y^{n} \cdot y^{7} = y^{n+7}

(am)n=amnaR,m,nN\boxed{(a^m)^n = a^{m \cdot n} \quad a \in \mathbb{R}, m, n \in \mathbb{N}}

(((am)n)r)s=amnrs\boxed{\left(((a^m)^n)^r\right)^s = a^{m \cdot n \cdot r \cdot s}}

Examples
  • (23)4=234=212=4096(2^3)^4 = 2^{3 \cdot 4} = 2^{12} = 4096
  • (x2)5=x25=x10(x^2)^5 = x^{2 \cdot 5} = x^{10}
  • ((3)4)2=(3)42=(3)8=6561((-3)^4)^2 = (-3)^{4 \cdot 2} = (-3)^8 = 6561
  • (a3)1=a31=a3(a^3)^1 = a^{3 \cdot 1} = a^3
  • ((12)2)3=(12)23=(12)6=164\left(\left(\dfrac{1}{2}\right)^2\right)^3= \left(\dfrac{1}{2}\right)^{2 \cdot 3} = \left(\dfrac{1}{2}\right)^6 = \dfrac{1}{64}
  • (ym)7=ym7=y7m(y^m)^7 = y^{m \cdot 7} = y^{7m}

(ab)n=anbna,bR,nN\boxed{(a \cdot b)^n = a^n \cdot b^n \quad a, b \in \mathbb{R}, n \in \mathbb{N}}

(xayb)n=xanybn\boxed{(x^a \cdot y^b)^n = x^{a \cdot n} \cdot y^{b \cdot n}}

Examples
  • (34)2=3242=916=144(3 \cdot 4)^2 = 3^2 \cdot 4^2 = 9 \cdot 16 = 144
  • (2x)3=23x3=8x3(2x)^3 = 2^3 \cdot x^3 = 8x^3
  • (52)4=(5)424=62516=10000(-5 \cdot 2)^4 = (-5)^4 \cdot 2^4 = 625 \cdot 16 = 10000
  • (ab)5=a5b5(ab)^5 = a^5 \cdot b^5
  • (12y)3=(12)3y3=18y3\left(\dfrac{1}{2} \cdot y\right)^3 = \left(\dfrac{1}{2}\right)^3 \cdot y^3 = \dfrac{1}{8}y^3
  • (xy2)4=x4(y2)4=x4y8(xy^2)^4 = x^4 \cdot (y^2)^4 = x^4 \cdot y^8

aman=amnm,nN,mn,aR{0}\boxed{\frac{a^m}{a^n} = a^{m-n} \quad m, n \in \mathbb{N}, m \geq n, a \in \mathbb{R} \setminus \{0\}}

Examples
  • 5753=573=54=625\dfrac{5^7}{5^3} = 5^{7-3} = 5^4 = 625
  • x8x5=x85=x3\dfrac{x^8}{x^5} = x^{8-5} = x^3
  • (2)6(2)2=(2)62=(2)4=16\dfrac{(-2)^6}{(-2)^2} = (-2)^{6-2} = (-2)^4 = 16
  • a10a10=a1010=a0=1(if a0)\dfrac{a^{10}}{a^{10}} = a^{10-10} = a^0 = 1 \quad \text{(if } a \neq 0\text{)}
  • 3532=352=33=27\dfrac{3^5}{3^2} = 3^{5-2} = 3^3 = 27
  • yn+4yn=y(n+4)n=y4\dfrac{y^{n+4}}{y^n} = y^{(n+4)-n} = y^4

(ab)n=anbnnN,bR{0}\boxed{\left(\frac{a}{b}\right)^n = \frac{a^n}{b^n} \quad n \in \mathbb{N}, b \in \mathbb{R} \setminus \{0\}}

Examples
  • (23)4=2434=1681\left(\dfrac{2}{3}\right)^4 = \dfrac{2^4}{3^4} = \dfrac{16}{81}
  • (52)3=5323=1258\left(\dfrac{5}{2}\right)^3 = \dfrac{5^3}{2^3} = \dfrac{125}{8}
  • (x4)2=x242=x216if xR\left(\dfrac{x}{4}\right)^2 = \dfrac{x^2}{4^2} = \dfrac{x^2}{16} \quad \text{if } x \in \mathbb{R}
  • (35)3=(3)353=27125\left(\dfrac{-3}{5}\right)^3 = \dfrac{(-3)^3}{5^3} = \dfrac{-27}{125}
  • (ab)5=a5b5if b0\left(\dfrac{a}{b}\right)^5 = \dfrac{a^5}{b^5} \quad \text{if } b \neq 0
  • (1x)n=1nxn=1xnif x0\left(\dfrac{1}{x}\right)^n = \dfrac{1^n}{x^n} = \dfrac{1}{x^n} \quad \text{if } x \neq 0

(ab)n=(ba)n=bnana,b0\boxed{\left(\frac{a}{b}\right)^{-n} = \left(\frac{b}{a}\right)^n = \frac{b^n}{a^n} \quad a, b \neq 0}

Examples
  • (23)4=(32)4=3424=8116\left(\dfrac{2}{3}\right)^{-4} = \left(\dfrac{3}{2}\right)^4 = \dfrac{3^4}{2^4} = \dfrac{81}{16}
  • (5x)2=(x5)2=x225if x0\left(\dfrac{5}{x}\right)^{-2} = \left(\dfrac{x}{5}\right)^2 = \dfrac{x^2}{25} \quad \text{if } x \neq 0
  • (14)3=(41)3=43=64\left(\dfrac{1}{4}\right)^{-3} = \left(\dfrac{4}{1}\right)^3 = 4^3 = 64
  • (ab)1=baif a,b0\left(\dfrac{a}{b}\right)^{-1} = \dfrac{b}{a} \quad \text{if } a, b \neq 0
  • (27)3=(72)3=73(2)3=3438=3438\left(\dfrac{-2}{7}\right)^{-3} = \left(\dfrac{7}{-2}\right)^3 = \dfrac{7^3}{(-2)^3} = \dfrac{343}{-8} = -\dfrac{343}{8}
  • (xy)5=y5x5if x,y0\left(\dfrac{x}{y}\right)^{-5} = \dfrac{y^5}{x^5} \quad \text{if } x, y \neq 0

xabc=xam=xn=z\boxed{x^{a^{b^c}} = x^{a^m}= x^n= z}

Note:

(xm)nxmn{(x^m)^n \neq x^{m^n}}

(x+y)nxn+yn{(x+y)^n \neq x^n+y^n}

Examples
  • 2231=223=28=2562^{2^{3^1}} = 2^{2^3} = 2^8 = 256
  • 3222=324=316=43, ⁣046, ⁣7213^{2^{2^2}} = 3^{2^4} = 3^{16} = 43,\!046,\!721
  • 5142=5116=51=55^{1^{4^2}} = 5^{1^{16}} = 5^1 = 5
  • 10315=1031=103=1, ⁣00010^{3^{1^5}} = 10^{3^1} = 10^3 = 1,\!000
  • 2321=232=29=5122^{3^{2^1}} = 2^{3^2} = 2^9 = 512
  • 4230=421=42=164^{2^{3^0}} = 4^{2^1} = 4^2 = 16

x2k2k=x={xif: x>00if: x=0xif: x<0\sqrt[2k]{x^{2k}} = |x| = \begin{cases} x & \text{if: } x > 0 \\ 0 & \text{if: } x = 0 \\ -x & \text{if: } x < 0 \end{cases}

!Remember!

Most commonly used powers

22=42^2 = 4 32=93^2 = 9 42=164^2 = 16 82=648^2 = 64
23=82^3 = 8 33=273^3 = 27 43=644^3 = 64 83=5128^3 = 512
24=162^4 = 16 34=813^4 = 81 52=255^2 = 25 92=819^2 = 81
25=322^5 = 32 35=2433^5 = 243 53=1255^3 = 125 93=7299^3 = 729
26=642^6 = 64 36=7293^6 = 729 54=6255^4 = 625 102=10010^2 = 100
27=1282^7 = 128 55=31255^5 = 3125 103=100010^3 = 1000
28=2562^8 = 256 62=366^2 = 36 112=12111^2 = 121
29=5122^9 = 512 63=2166^3 = 216 113=133111^3 = 1331
210=10242^{10} = 1024 64=12966^4 = 1296 122=14412^2 = 144
72=497^2 = 49 123=172812^3 = 1728
73=3437^3 = 343
74=24017^4 = 2401

Radicals in R\mathbb{R}

Fundamental Identity

y=xn    yn=x\boxed{y = \sqrt[n]{x} \iff y^n = x }

Where:

  • xx: radicand (xR,x0x \in \mathbb{R}, x \geq 0 if nn is even)
  • nn: index (nN,n2n \in \mathbb{N}, n \geq 2)
  • yy: root (y0y \geq 0 if nn is even)

abn=anbn\boxed{\sqrt[n]{a \cdot b} = \sqrt[n]{a} \cdot \sqrt[n]{b}}

If nn is even, then a0a \geq 0 and b0b \geq 0.

Examples
  • 49=49=23=6\sqrt{4 \cdot 9} = \sqrt{4} \cdot \sqrt{9} = 2 \cdot 3 = 6
  • 8273=83273=23=6\sqrt[3]{8 \cdot 27} = \sqrt[3]{8} \cdot \sqrt[3]{27} = 2 \cdot 3 = 6
  • 16814=164814=23=6\sqrt[4]{16 \cdot 81} = \sqrt[4]{16} \cdot \sqrt[4]{81} = 2 \cdot 3 = 6
  • xy=xyif x0, y0\sqrt{x \cdot y} = \sqrt{x} \cdot \sqrt{y} \quad \text{if } x \geq 0,\ y \geq 0
  • a5b105=a55b105=ab2\sqrt[5]{a^5 \cdot b^{10}} = \sqrt[5]{a^5} \cdot \sqrt[5]{b^{10}} = a \cdot b^2
  • 8643=83643=(2)4=8\sqrt[3]{-8 \cdot 64} = \sqrt[3]{-8} \cdot \sqrt[3]{64} = (-2) \cdot 4 = -8

abn=anbnb0\boxed{\sqrt[n]{\frac{a}{b}} = \frac{\sqrt[n]{a}}{\sqrt[n]{b}} \quad b \neq 0}

If nn is even, then a0a \geq 0 and b>0b > 0.

Examples
  • 916=916=34\sqrt{\dfrac{9}{16}} = \dfrac{\sqrt{9}}{\sqrt{16}} = \dfrac{3}{4}
  • 271253=2731253=35\sqrt[3]{\dfrac{27}{125}} = \dfrac{\sqrt[3]{27}}{\sqrt[3]{125}} = \dfrac{3}{5}
  • 1814=14814=13\sqrt[4]{\dfrac{1}{81}} = \dfrac{\sqrt[4]{1}}{\sqrt[4]{81}} = \dfrac{1}{3}
  • x5325=x55325=x2if xR\sqrt[5]{\dfrac{x^5}{32}} = \dfrac{\sqrt[5]{x^5}}{\sqrt[5]{32}} = \dfrac{x}{2} \quad \text{if } x \in \mathbb{R}
  • ab=abif a0, b>0\sqrt{\dfrac{a}{b}} = \dfrac{\sqrt{a}}{\sqrt{b}} \quad \text{if } a \geq 0,\ b > 0
  • 8273=83273=23\sqrt[3]{\dfrac{-8}{27}} = \dfrac{\sqrt[3]{-8}}{\sqrt[3]{27}} = \dfrac{-2}{3}

anm=amnm,nN\boxed{\sqrt[m]{\sqrt[n]{a}} = \sqrt[m \cdot n]{a} \quad m, n \in \mathbb{N}}

If mnm \cdot n is even, then a0a \geq 0.

arsnm=amnsr\boxed{\sqrt[m]{\sqrt[n]{\sqrt[s]{\sqrt[r]{a}}}} = \sqrt[m \cdot n \cdot s \cdot r]{a}}

Examples
  • 832=86=236=23/6=21/2=2\sqrt[2]{\sqrt[3]{8}} = \sqrt[6]{8} = \sqrt[6]{2^3} = 2^{3/6} = 2^{1/2} = \sqrt{2}
  • x43=x12for x0\sqrt[3]{\sqrt[4]{x}} = \sqrt[12]{x} \quad \text{for } x \geq 0
  • 16=1622=164=2\sqrt{\sqrt{16}} = \sqrt[2]{\sqrt[2]{16}} = \sqrt[4]{16} = 2
  • a5=a10if a0\sqrt[5]{\sqrt{a}} = \sqrt[10]{a} \quad \text{if } a \geq 0
  • 6434=6412=2612=26/12=21/2=2\sqrt[4]{\sqrt[3]{64}} = \sqrt[12]{64} = \sqrt[12]{2^6} = 2^{6/12} = 2^{1/2} = \sqrt{2}
  • x=x222=x8for x0\sqrt{\sqrt{\sqrt{x}}} = \sqrt[2]{\sqrt[2]{\sqrt[2]{x}}} = \sqrt[8]{x} \quad \text{for } x \geq 0

(an)m=amn\boxed{\left(\sqrt[n]{a}\right)^m = \sqrt[n]{a^m}}

xacab=xcbIf ab is even, then xR0+ \boxed{\sqrt[ab]{x^{ac}} = \sqrt[b]{x^c} \quad \text{If } ab \text{ is even, then } x \in \mathbb{R}_0^+}

Examples
  • (23)6=263=643=4\left(\sqrt[3]{2}\right)^6 = \sqrt[3]{2^6} = \sqrt[3]{64} = 4
  • (5)4=54=625=25\left(\sqrt{5}\right)^4 = \sqrt{5^4} = \sqrt{625} = 25
  • (34)2=324=94\left(\sqrt[4]{3}\right)^2 = \sqrt[4]{3^2} = \sqrt[4]{9}
  • (xn)3=x3nif x0 when n is even\left(\sqrt[n]{x}\right)^3 = \sqrt[n]{x^3} \quad \text{if } x \geq 0 \text{ when } n \text{ is even}
  • (325)3=(32)35=327685=8\left(\sqrt[5]{-32}\right)^3 = \sqrt[5]{(-32)^3} = \sqrt[5]{-32768} = -8
  • (a2+b2)2=(a2+b2)2=a2+b2=a2+b2\left(\sqrt{a^2 + b^2}\right)^2 = \sqrt{(a^2 + b^2)^2} = |a^2 + b^2| = a^2 + b^2

xaxbxcpmn=x(am+b)p+cnmp \sqrt[n]{x^{a}\cdot \sqrt[m]{x^{b}\cdot \sqrt[p]{x^c}}} = \sqrt[nmp]{x^{(am + b)p+c}}

xa÷xb÷xcpmn=x(amb)p+cnmp \sqrt[n]{x^{a}\div \sqrt[m]{x^{b}\div \sqrt[p]{x^c}}} = \sqrt[nmp]{x^{(am - b)p+c}}

xyzpnm=xmymnznmp \sqrt[m]{x \cdot \sqrt[n]{y \cdot \sqrt[p]{z}}} = \sqrt[m]{x} \cdot \sqrt[m \cdot n]{y} \cdot \sqrt[n \cdot m \cdot p]{z}

xaybzcpnm=xamybmnzcnmp \sqrt[m]{x^a \cdot \sqrt[n]{y^b \cdot \sqrt[p]{z^c}}} = \sqrt[m]{x^a} \cdot \sqrt[m \cdot n]{y^b} \cdot \sqrt[n \cdot m \cdot p]{z^c}

xa÷yb÷zc÷wd÷ve÷ufsrqpnm=axmczmnpevmnpqrbymndwmnpqfumnpqrs \sqrt[m]{x^{a}\div \sqrt[n]{y^{b}\div \sqrt[p]{z^{c}\div \sqrt[q]{w^{d}\div \sqrt[r]{v^{e}\div \sqrt[s]{u^f}}}}}} = \frac{\cfrac{a}{x^m} \cdot \cfrac{c}{z^{mnp}} \cdot \cfrac{e}{v^{mnpqr}}}{\cfrac{b}{y^{mn}} \cdot \cfrac{d}{w^{mnpq}} \cdot \cfrac{f}{u^{mnpqrs}}}

!Remember!
Radical Type Simplified Form Radical Form
Square Roots 222\sqrt{2} 8\sqrt{8}
323\sqrt{2} 18\sqrt{18}
424\sqrt{2} 32\sqrt{32}
525\sqrt{2} 50\sqrt{50}
333\sqrt{3} 27\sqrt{27}
434\sqrt{3} 48\sqrt{48}
535\sqrt{3} 75\sqrt{75}
353\sqrt{5} 45\sqrt{45}
454\sqrt{5} 80\sqrt{80}
252\sqrt{5} 20\sqrt{20}
Cube Roots 2232\sqrt[3]{2} 163\sqrt[3]{16}
3233\sqrt[3]{2} 543\sqrt[3]{54}
2332\sqrt[3]{3} 243\sqrt[3]{24}
3333\sqrt[3]{3} 813\sqrt[3]{81}
Approximate Values 2\sqrt{2} 1.4142...1.4142...
3\sqrt{3} 1.732...1.732...
5\sqrt{5} 2.236...2.236...

xmypn=xmnypnx^m \cdot \sqrt[n]{y^p} = \sqrt[n]{x^{mn} \cdot y^p}

xmxn=xn+mmn\sqrt[m]{x} \cdot \sqrt[n]{x} = \sqrt[mn]{x^{n+m}}

xmxn=xnmmn,x0\frac{\sqrt[m]{x}}{\sqrt[n]{x}} = \sqrt[mn]{x^{n-m}}, \, x \neq 0

1zcybxa=1x1y1zcba\sqrt[a]{\frac{\sqrt[b]{\cfrac{\sqrt[c]{\cfrac{1}{z}}}{y}}}{x}} = \sqrt[a]{\frac{1}{x}\cdot \sqrt[b]{\frac{1}{y}\cdot \sqrt[c]{\frac{1}{z}}}}

abcpnmdefpnm=adbecfpnm\frac{\sqrt[m]{a\cdot \sqrt[n]{b\cdot \sqrt[p]{c}} } }{\sqrt[m]{d\cdot \sqrt[n]{e\cdot \sqrt[p]{f}} } } = \sqrt[m]{\frac{a}{d}\cdot \sqrt[n]{\frac{b}{e}\cdot \sqrt[p]{\frac{c}{f}}}}

xyzpnm=xmynzp \sqrt[m]{x^{ \sqrt[n]{y^{ \sqrt[p]{z}}}}} = \sqrt[m]{x}^{\sqrt[n]{y}^{\sqrt[p]{z}}}

  1. Expressions with a Fixed Number of Radicals

xnnnnm radicals=xnm\underbrace{\sqrt[n]{ \sqrt[n]{ \sqrt[n]{ \dots \sqrt[n]{x}}}}}_{\text{m radicals}} = \sqrt[n^m]{x}

xxx...xnnnnm radicals=xnm1n1nm\underbrace{\sqrt[n]{x \cdot \sqrt[n]{x \cdot \sqrt[n]{x \cdot ...\cdot \sqrt[n]{x}}}}}_{\text{m radicals}} = \sqrt[n^m]{x^{\cfrac{n^m - 1}{n-1}}}

x÷x÷x÷...÷xnnnnm radicals={xnm1n+1nmif m is even,xnm+1n+1nmif m is odd. \underbrace{\sqrt[n]{x\div \sqrt[n]{x\div \sqrt[n]{x\div ... \div \sqrt[n]{x}}}}}_{\text{m radicals}} = \begin{cases} \sqrt[n^m]{x^{\cfrac{n^m - 1}{n + 1}}} & \text{if m is even}, \\ \sqrt[n^m]{x^{\cfrac{n^m + 1}{n + 1}}} & \text{if m is odd}. \end{cases}

  1. Expressions with Infinite Radicals

x(x+1)+x(x+1)+x(x+1)+=x+1\sqrt{x\cdot(x+1)+ \sqrt{x\cdot(x+1)+ \sqrt{x\cdot(x+1)+ \dots } }} = x+1

x(x+1)x(x+1)x(x+1)=x\sqrt{x\cdot(x+1)- \sqrt{x\cdot(x+1)- \sqrt{x\cdot(x+1)- \dots } }} = x

xxx...nnn=xn1\sqrt[n]{x\cdot \sqrt[n]{x\cdot \sqrt[n]{x\cdot...} }} = \sqrt[n-1]{x}

x÷x÷x÷...nnn=xn+1\sqrt[n]{x\div \sqrt[n]{x\div \sqrt[n]{x\div...} }} = \sqrt[n+1]{x}

aaaamnmn=am+1mn1 \quad \sqrt[n]{a \cdot \sqrt[m]{a \cdot \sqrt[n]{a \cdot \sqrt[m]{a\cdot \dots} }}} = \sqrt[m \cdot n - 1]{a^{m+1}}

ababmnmn=ambmn1\quad \sqrt[n]{a \cdot \sqrt[m]{b \cdot \sqrt[n]{a \cdot \sqrt[m]{b\cdot \dots} }}} = \sqrt[m \cdot n - 1]{a^m \cdot b}

a+a+a+=1+4a+12\quad \sqrt{a + \sqrt{a + \sqrt{a + \dots}}} = \frac{1 + \sqrt{4a + 1}}{2}

aaa=1+4a+12\quad \sqrt{a - \sqrt{a - \sqrt{a - \dots}}} = \frac{-1 + \sqrt{4a + 1}}{2}

  1. Infinite Power Towers

xxx...xn=nx=nn;x0x^{x^{x^{{.}^{{.}^{{.}^{x^n}}}}}} = n \rightarrow x = \sqrt[n]{n}; \, x \neq 0

babababa...=cb=c\sqrt[a]{b}^{\sqrt[a]{b}^{\sqrt[a]{b}^{\sqrt[a]{b}^{.^{.^{.}}}}}} = c \rightarrow b = c

am=an    m=n;a>0a1a^m = a^n \implies m = n; \quad a > 0 \land a \neq 1

Examples
  • 2x=25    x=52^{x} = 2^{5} \implies x = 5
  • 32y=38    2y=8    y=43^{2y} = 3^{8} \implies 2y = 8 \implies y = 4
  • 103z1=10z+7    3z1=z+7    z=410^{3z - 1} = 10^{z + 7} \implies 3z - 1 = z + 7 \implies z = 4
  • (12)t=(12)4    t=4\left(\frac{1}{2}\right)^{t} = \left(\frac{1}{2}\right)^{4} \implies t = 4
  • 7a+2=72a3    a+2=2a3    a=57^{a+2} = 7^{2a - 3} \implies a + 2 = 2a - 3 \implies a = 5
  • e3x=ex+10    3x=x+10    x=5e^{3x} = e^{x + 10} \implies 3x = x + 10 \implies x = 5

am=bm    a=b;m0,a>0b>0a^m = b^m \implies a = b; \quad m \neq 0, a > 0 \land b > 0

Examples
  • x3=53    x=5x^3 = 5^3 \implies x = 5
  • (2y)4=64    2y=6    y=3(2y)^4 = 6^4 \implies 2y = 6 \implies y = 3
  • a7=b7    a=ba^7 = b^7 \implies a = b
  • (x+1)2=(3x1)2(x+1)^2 = (3x - 1)^2 with x+1>0x+1 > 0, 3x1>0    x+1=3x1    x=13x - 1 > 0 \implies x+1 = 3x - 1 \implies x = 1
  • (4z)5=(2z+6)5    4z=2z+6    z=3(4z)^5 = (2z + 6)^5 \implies 4z = 2z + 6 \implies z = 3
  • (a2)6=(32)6    a2=32    a=3\left(\frac{a}{2}\right)^6 = \left(\frac{3}{2}\right)^6 \implies \frac{a}{2} = \frac{3}{2} \implies a = 3

am=bn    m=n=0 a^m = b^n \implies m = n = 0

Examples
  • 2x=7y2^x = 7^y and 2x=1    x=02^x = 1 \implies x = 0, 7y=1    y=07^y = 1 \implies y = 0
  • 3a+1=5b23^{a+1} = 5^{b-2} and the value is 1 → a+1=0a+1 = 0, b2=0    a=1b-2 = 0 \implies a = -1, b=2b = 2
  • 10m=9n=1    m=010^m = 9^n = 1 \implies m = 0, n=0n = 0
  • (13)2x=4y+1=1    2x=0\left(\frac{1}{3}\right)^{2x} = 4^{y+1} = 1 \implies 2x = 0, y+1=0    x=0y+1 = 0 \implies x = 0, y=1y = -1
  • πt=es=1    t=0\pi^{t} = e^{s} = 1 \implies t = 0, s=0s = 0
  • 6x3=82y=1    x3=06^{x-3} = 8^{2-y} = 1 \implies x - 3 = 0, 2y=0    x=32 - y = 0 \implies x = 3, y=2y = 2

aa=bb    a=b;a0b0a^a = b^b \implies a = b; \quad a \neq 0 \land b \neq 0

Examples
  • xx=22    x=2x^x = 2^2 \implies x = 2
  • yy=33    y=3y^y = 3^3 \implies y = 3
  • zz=11    z=1z^z = 1^1 \implies z = 1
  • aa=(12)1/2    a=12a^a = \left(\frac{1}{2}\right)^{1/2} \implies a = \frac{1}{2}
  • bb=44    b=4b^b = 4^4 \implies b = 4
  • tt=55    t=5t^t = 5^5 \implies t = 5

aaa+m=aaa+n    m=na^{a^{a+m}} = a^{a^{a+n}} \implies m = n

Examples
  • 222+m=222+3    m=32^{2^{2+m}} = 2^{2^{2+3}} \implies m = 3
  • 333+x=333+1    x=13^{3^{3+x}} = 3^{3^{3+1}} \implies x = 1
  • 222+y=222+y+0    y=y2^{2^{2+y}} = 2^{2^{2+y+0}} \implies y = y (trivially valid: m=nm = n)
  • 444+a=444+0    a=04^{4^{4+a}} = 4^{4^{4+0}} \implies a = 0
  • 555+t=555+2    t=25^{5^{5+t}} = 5^{5^{5+2}} \implies t = 2
  • 101010+z=101010+7    z=710^{10^{10+z}} = 10^{10^{10+7}} \implies z = 7

xxm=m    x=mmx^{x^m} = m \implies x = \sqrt[m]{m}

Equations with Variables in the Exponent

  1. Exponential Form:

xx=an    x=ax^x = a^n \implies x = a

  1. Radical Form:

xx=n    x=nxx^x = n \implies x = \sqrt[x]{n}