Question

Factor: x2 - 13x + 36

Answer 1

the way to do this is to ask : what two factors of 36 add up to -13

Answer 2

(x + b)(x + d) = 0 is what you want to set up
then as @thomasj said you want to figure out what two factors of 36 add up to -13. meaning what
b*d = 36 and also b+d = -13

Answer 3

continue writing the factors, and you will see what you need