Question 21896
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.