SOLUTION: Please show how to work this problem using the ac method (7y^2+16y-15) (Factoring).

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a=7,b=16,c=-15
ac = 7(-15) = -105
Find two integers whose product is ac=-105
and whose sum is b=16
Try -5 and +21
Rewrite the original problem as follows:
7x^2 + 21x +-5x -15
Factor the 1st two terms then the last two, as follows:
7x(x+3)-5(x+3)
Factor again, as follows:
(x+3)(7x-5)
Cheers,
Stan H.