# SOLUTION: x^-2-64y^-2 ___________ 9y-72x i'm having trouble with this one.

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 Algebra: Expressions involving variables, substitution Solvers Lessons Answers archive Quiz In Depth

 Click here to see ALL problems on Expressions-with-variables Question 28021: x^-2-64y^-2 ___________ 9y-72x i'm having trouble with this one.Answer by sdmmadam@yahoo.com(530)   (Show Source): You can put this solution on YOUR website!x^-2-64y^-2 ___________ 9y-72x =[(1/x^2)-(64/y^2)]/(9y-72x) [using a^-m = (1/a^m)] =(y^2-64x^2)/[9x^2y^2(y-8x)] [finding the lcm in the nr and taking out 9 in the dr] =[(y+8x)(y-8x)]/[9x^2y^2(y-8x)] [using formula p^2-q^2 = (p+q)(p-q) and here p =y and q = 8x] =(y+8x)/9x^2y^2 (cancelling (y-8x)in the nr and in the dr)