Some one factor x^2-x-72

Think of products that equal to 72

When you find those numbers add or subtract those numbers to see if you get the value in the center

9*8=72

Make 9 a negative (-9) and 8 a negative 9 in the first parenthesis and positive 8 in the second you will get

-8x+9x=-x

(x-9) (x+8)