Question 78705: Factor completely
9x^2 + 24xy - 9y^2
I know the GCF is 3, but I don't know what to do with the two different variables. Thank you Found 2 solutions by checkley75, stanbon:Answer by checkley75(3666) (Show Source):
You can put this solution on YOUR website! Factor completely
9x^2 + 24xy - 9y^2
=3(3x^2+8xy-3y^2)
Think of two numbers whose product is 3*-3=-9 and whose sum is 8
The numbers are +9 and -1
So rewrite the problem putting 9xy-1xy in place of 8xy
=3(3x^2+9xy-xy-3y^2)
Factor the 1st two and the last two terms separately to get:
=3(3x(x+3y)-y(x+3y))
Factor out the common factor to get:
=3(x+3y)(3x-y)
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Cheers,
Stan H.
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