Evaluate

Algebra Level 1

( 1 125 ) 2 3 \displaystyle { \left( -\cfrac { 1 }{ 125 } \right) }^{ -\frac{ 2 }{ 3 } } can be written as __________ . \text{\_\_\_\_\_\_\_\_\_\_}.

25 -25 1 25 \displaystyle -\frac { 1 }{ 25 } 1 25 \displaystyle \frac { 1 }{ 25 } 25 25

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7 solutions

Soumo Mukherjee
Dec 19, 2014

One must know some properties of exponent to solve this.

( 1 125 ) 2 / 3 = ( 125 ) 2 / 3 = [ ( 125 ) 1 3 ] 2 = [ ( 5 3 ) 1 3 ] 2 = ( 5 ) 2 = 25 { \left( -\cfrac { 1 }{ 125 } \right) }^{ { -2 }/{ 3 } }={ \left( -125 \right) }^{ { 2 }/{ 3 } }={ \left[ { \left( -125 \right) }^{ \cfrac { 1 }{ 3 } } \right] }^{ 2 }={ \left[ { \left( -{ 5 }^{ 3 } \right) }^{ \cfrac { 1 }{ 3 } } \right] }^{ 2 }=(-5 )^{ 2 }=25

You goofed, not putting the last 5 in parentheses. 5 2 = 25 -5^2 = -25 , but ( 5 ) 2 = 25 (-5)^2 = 25 .

Whitney Clark - 5 years, 10 months ago

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Thanks! I've edited it in.

Calvin Lin Staff - 5 years, 8 months ago
Chew-Seong Cheong
Aug 16, 2015

( 1 125 ) 2 3 = ( 5 3 ) 2 3 = ( 5 ) ( 3 ) ( 2 3 ) = ( 5 ) 2 = 25 \left(-\dfrac{1}{125} \right)^{-\frac{2}{3}} = \left(- 5^{-3} \right)^{-\frac{2}{3}} = (-5)^{(-3)\left(-\frac{2}{3}\right)} = (-5)^2 = \boxed{25}

Jack Rawlin
Dec 22, 2014

( 1 125 ) 2 3 (-\frac {1}{125})^{\frac {-2}{3}}

1 125 -\frac {1}{125} can be written as ( 5 ) 3 (-5)^{-3}

So ( 1 125 ) 2 3 (-\frac {1}{125})^{\frac {-2}{3}} becomes ( ( 5 ) 3 ) 2 3 ((-5)^{-3})^{\frac {-2}{3}}

Since ( n x ) y = n x y (n^x)^y = n^{xy} we can write it as

( 5 ) 2 = 25 (-5)^2 = 25

So the answer is 25 25

Mehul Arora
Dec 18, 2014

According to the question, (-1/5)^3*-2/3

According to the law of exponents, (a^m)^n= a^mn

Therefore, The expression is(-1/5)^-2 because (-2/3*3=-2)

=-5^2 because [(1/a)]^-m=a^m

Answer= 25

Jesse Nieminen
Aug 17, 2015

( 1 125 ) 2 3 = ( ( 5 ) 3 ) 2 3 = ( 5 ) 2 = 25 { {\left(-\frac{1}{125}\right)}^{ -\frac{2}{3} } ={ {\left(\left({-5}\right)^{ -3}\right)}^{ -\frac{2}{3} } } = \left({-5}\right)^{2} = \underline{25} }

Moderator note:

Note that the rules of exponents do not necessarily hold for non-positive integers.

For example, ( ( 2 ) 2 ) 1 2 = 4 1 2 = 2 \left( (-2) ^ 2\right) ^ \frac{1}{2} = 4 ^ \frac{1}{2} = 2 , and it not equal to ( 2 ) 2 × 1 2 = 2 (-2) ^ { 2 \times \frac{1}{2}} = -2 .

Hadia Qadir
Aug 17, 2015

-1/125)^-2/3 = (-1/125)^-1(2/3) (-125)^2/3 (-5)^2 25

Ahmed Brisha
Aug 16, 2015

(-1/125)^-2/3=(-125)^2/3=cubic root of 125^2 =cubic root of 5^6 =5 ^(6/3)=5^2=25

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