SOLUTION: Steps to this pleasee Simplify x^2/3-13x^1/3-30=0

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Question 720553: Steps to this pleasee
Simplify x^2/3-13x^1/3-30=0

Answer by jsmallt9(3758) About Me  (Show Source):
You can put this solution on YOUR website!
x%5E%282%2F3%29-13x%5E%281%2F3%29-30=0
Since the exponent of x%5E%282%2F3%29 is exactly twice the exponent of x%5E%281%2F3%29, this equation is in what is called quadratic form. And these quadratic form equations can be solved in much the same way as regular quadratic equations.

To see the "quadratic-ness" of this equation it can help to use a temporary variable. Set it to the base and lower exponent. So:
Let q+=+x%5E%281%2F3%29.
Then q%5E2+=+%28x%5E%281%2F3%29%29%5E2+=+x%5E%282%2F3%29.
Substituting these into our equation we get:
q%5E2-13q-30=0
This is obviously a quadratic equation. It's already got a zero on one side. And it factors pretty easily:
(q-10)(q-3) = 0
From the Zero Product Property:
q-10 = 0 or q-3 = 0
Solving these:
q = 10 or q = 3

Of course we're not interested in solutions for q. We're interested in solutions for x. So we substitute back:
x%5E%281%2F3%29+=+10 or x%5E%281%2F3%29+=+3
We have a little more work to do to solve for x. The quick way is to cube both sides:
%28x%5E%281%2F3%29%29%5E3+=+%2810%29%5E3 or %28x%5E%281%2F3%29%29%5E3+=+%283%29%5E3
which simplifies to:
x = 1000 or x = 27

P.S. Once you have done a few of these quadratic form equations you will no longer need a temporary variable. You will learn to see how to go directly from:
x%5E%282%2F3%29-13x%5E%281%2F3%29-30=0
to
%28x%5E%281%2F3%29-10%29%28x%5E%281%2F3%29-3%29=0
to
x%5E%281%2F3%29-10+=+0 or x%5E%281%2F3%29-3=0
etc.

P.S. Please put fractional exponents in parentheses.