SOLUTION: How do you solve: x^-2=9

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Question 69787: How do you solve:
x^-2=9

Answer by bucky(2189) About Me  (Show Source):
You can put this solution on YOUR website!
Your problem is:
x%5E%28-2%29+=+9
The negative exponent means that the term raised to that negative value can be changed
into a fraction having 1 as the numerator and the term with a positive exponent as the
denominator. Easier to show by an example than to explain it.
Think "I can change x%5E%28-2%29 into x%5E2%29 by making %28x%5E2%29 the denominator
of a fraction that has 1 as its numerator." When you do that your problem becomes:
1%2Fx%5E2+=+9
Then you can eliminate the denominator if you multiply both sides by x%5E2
If you do that multiplication on the left side you have a fraction that has x%5E2
in both the numerator and denominator. This is equivalent to 1. On the right side the multiplication results in 9%2Ax%5E2 and the problem becomes:

+1+=+9x%5E2
Dividing both sides by 9 gives:
1%2F9+=+x%5E2
Now just take the square root of both sides. Notice that sqrt%281%2F9%29+=+1%2F3 because
%281%2F3%29%2A%281%2F3%29+=+%281%2F9%29. Also notice that both the positive and negative forms
of 1%2F3 are needed because when either is squared they produce a positive value
of 1%2F9
The two answers to this problem are:
1%2F3+=+x and -1%2F3+=+x
You can check this by putting each of these answers (positive and negative) one at a time
into the equation:
1%2Fx%5E2+=+9
and see that with these values the left side of the equation equals 9.