If (x-1)^(2/3) =25 then x equals what?

1 Answer
Jun 2, 2018

x=126

Explanation:

This problem might appear scary because to isolate x, you need to so some tricky stuff with exponents.

But if you think about it, we can cancel out the 2/3 by raising each side to 3/2, because when you raise an exponent to an exponent it serves to multiply the two, and 2/3*3/2=1.

Based on this, we can raise 25 to the power of 3/2, as well as (x-1)^(2/3) in order to get the equation

(x-1)^(2/3*3/2)=25^(3/2)
(x-1)=125
x=126

Sure enough, if you plug in 126 for x, you get 25 as your output:
![https://www.desmos.com/calculator/czkefr2lhb](useruploads.socratic.org)