Answer:
(x-12)(x+7)
Explanation:
x^2 - 5x - 84
You find the factors of 84:
1,84; 2,42; 3,28; 4,21; 6,14; 7,12
7 and 12 are 5 apart, so we use them:
(x - 12)(x + 7)
The 12 is negative because it's greater than 7, and the coefficient of x is negative 5.