00:01
In this problem, we're being asked to factor the given trinomial using the ac method.
00:05
So we have to begin by multiplying the first and last coefficients.
00:09
Remember, we don't see a coefficient.
00:10
It's imaginary one.
00:12
So we'll multiply 1 times negative 18, which is equal to negative 18.
00:17
So now we have to find two numbers that multiply the negative 18 that will add to our middle coefficient of 7.
00:24
Well, in this case, i'm thinking 9 and negative 2.
00:28
Because 9 times negative 2 is negative 18, and 9 plus negative 2 is positive 7.
00:35
Perfect.
00:36
So now we're going to rewrite our problem, but in place of positive 7x, we're going to substitute in 9x minus 2x...