We subtract 7x from both sides so that the RHS would be 0.
x² - 7x - 18 = 0
We look for two numbers with a product of 18 and a difference of 7.
18 - 1 = 17 X
9 - 2 = 7 √
6 - 3 = 3 X
So,
(x-9)(x+2)=0
This would mean that x=9 or x =-2 since one of thee factors need to be 0. (in order to know this, equate both factors to 0.)
Check:
If x = 9
9² - 7(9) - 18 = 0
81 - 63 - 18 = 0
18 - 18 = 0
0 = 0 This is indeed TRUE
If x = -2
(-2)² - 7(-2) -18 = 0
4 + 14 - 18 = 0
18 - 18 = 0
0 = 0 This indeed TRUE
