SOLUTION: Solve a) x^(2/3) + x^(1/3) - 2 = 0 Thanks so much in advance:)

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Question 818015: Solve
a) x^(2/3) + x^(1/3) - 2 = 0
Thanks so much in advance:)

Answer by jsmallt9(3758) About Me  (Show Source):
You can put this solution on YOUR website!
x%5E%282%2F3%29+%2B+x%5E%281%2F3%29+-+2+=+0
Since the exponent of the first term, 2/3, is exactly twice the exponent in the middle, 1/3, this equation is in what is known as quadratic form. Quadratic form equations have the same underlying structure as a "pure" quadratic equation and can be solved using the same techniques.

To see this more easily, it can be helpful to use a temporary variable:
Let q+=+x%5E%281%2F3%29. This makes q%5E2+=+%28x%5E%281%2F3%29%29%5E2+=+x%5E%282%2F3%29.
Substituting these in to the equation we get:
q%5E2%2Bq-2=0
This is obviously a quadratic equation. It will factor:
%28q%2B2%29%28q-1%29=0
From the Zero Product Property:
q+2 = 0 or q-1 = 0
Solving these:
q = -2 or q = 1

Of course we are not interested in solutions for our made-up variable q. So we replace the q's:
x%5E%281%2F3%29+=+-2 or x%5E%281%2F3%29+=+1
To solve these we just cube both sides of both equations:
x+=+-8 or x+=+1

P.S. After doing several of these quadratic form equations you will no longer need the temporary variable. You will start seeing how to go directly from:
x%5E%282%2F3%29+%2B+x%5E%281%2F3%29+-+2+=+0
to
%28x%5E%281%2F3%29%2B2%29%28x%5E%281%2F3%29-1%29+=+0
to
x%5E%281%2F3%29%2B2+=+0 or x%5E%281%2F3%29-1+=+0
etc.