Answer:
(x - 7)(x - 8)
Explanation:
To factorise the quadratic
Consider the factors of the constant term (+ 56) which sum to give the coefficient of the x- term (- 15)
The factors are - 7 and - 8, since
- 7 × - 8 = + 56 and - 7 - 8 = - 15, hence
x² - 15x + 56 = (x - 7)(x - 8)