Question 78705
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.