7x2 plus 7x5 = 49
7x2
7x2 + 68xy - 20y2
(7x2 + 9)(4x - 1)
You can take 7x2 out of both of those, leaving 5x4 and 1.
I suppose you mean, how do you factor it. 7x2 - 9x - 10 = (7x + 5)(x - 2).
(x - 3)(7x + 2)
(7x + 4)(x - 5)
(7x + 6)(x - 2)
(7x + 4)(x - 1)
7x2 + 7x - 14 = 7(x2 + x - 2) = 7(x + 2)(x - 1)
(x - 2)(7x + 15)