What is the factorization of x2-15x+56...I think it is (x-7)(x+8)...please help

What 2 numbers sum to -15 and multiply to 56?

The coefficients derive from
x + y = -15 and xy = 56
Then, x + 56/x = -15
Then, x^2 + 15x + 56 = 0
Then, x = [-15+/-sqrt(225 - 224)]/2
......x = [-15+/-1]/2 yielding
x = -8 and y = -7 or
(x - 8)(x - 7) = x^2 - 15 + 56.