SOLUTION: x^2/3 - x^1/3 - 20 = 0

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Question 363806: x^2/3 - x^1/3 - 20 = 0
Found 2 solutions by amoresroy, robertb:
Answer by amoresroy(361) About Me  (Show Source):
You can put this solution on YOUR website!
x^2/3 - x^1/3 - 20 = 0
Let y = x^1/3
Substitute x^1/3 = y
y2 - y - 20 = 0
Solve by factoring
(y-5) (y+4) = 0
y-5 = 0
y = 5
Since y = x^1/3
Then x^1/3 = 5
Raise both sides by exponent 3 to get x
[x^1/3 = 5]^3
x = 5*5*5
x = 125

Answer by robertb(5830) About Me  (Show Source):
You can put this solution on YOUR website!
x%5E%282%2F3%29+-+x%5E%281%2F3%29+-+20+=+0,
%28x%5E%281%2F3%29-5%29%28x%5E%281%2F3%29%2B4%29+=+0,
x%5E%281%2F3%29-5=+0 or x%5E%281%2F3%29%2B4+=+0. Thus x+=+5%5E3+=+125, or x+=+%28-4%29%5E3+=+-64.
To check:
, and
%28125%29%5E%282%2F3%29-%28125%29%5E%281%2F3%29+-+20+=+5%5E2+-+5-20+=+25-5-20+=+0.