SOLUTION: I can't understand how the solution set to (x-4)^(2/3)=16 is {-60,68}? I need precise step-by-step info, because I am looking at an example problem, and I'm still not getting it.

Algebra ->  College  -> Linear Algebra -> SOLUTION: I can't understand how the solution set to (x-4)^(2/3)=16 is {-60,68}? I need precise step-by-step info, because I am looking at an example problem, and I'm still not getting it.      Log On


   



Question 876668: I can't understand how the solution set to (x-4)^(2/3)=16 is {-60,68}? I need precise step-by-step info, because I am looking at an example problem, and I'm still not getting it.
Found 2 solutions by Alan3354, Edwin McCravy:
Answer by Alan3354(69443) About Me  (Show Source):
You can put this solution on YOUR website!
(x-4)^(2/3)=16
------
Take the sq root of both sides
(x-4)^(1/3)= 4
Cube both sides
x-4 = 64
x = 68
-------------
Do the same with sqrt(16) = -4

Answer by Edwin McCravy(20055) About Me  (Show Source):
You can put this solution on YOUR website!
Here's an alternate way.  Slightly different:

matrix%282%2C1%2C%22%22%2C%0D%0A%0D%0A%0D%0A%28x-4%29%5E%282%2F3%29%29matrix%282%2C1%2C%22%22%2C%22%22=%22%22%29matrix%282%2C1%2C%22%22%2C16%29

We want to make the exponent 2%2F3 become a whole
number. So we raise both sides to the 3 power. That is,
we cube both sides:

%28%28x-4%29%5E%282%2F3%29%29%5E3%22%22=%22%2216%5E3

%28x-4%29%5E2%22%22=%22%224096

Use the principle of square roots:

x-4%22%22=%22%22%22%22+%2B-+sqrt%284096%29

x-4%22%22=%22%22%22%22+%2B-+64

x-4 = 64;      x-4 = -64
  x = 68;        x = -68

Edwin