9(x+2)(x+1)-2(x+2)-4(x+1)=0
I'm in the middle of solving an equation. I know that you have to FOIL but how did they get 9(x^2+3x+2)-(4x+4)=0 ?
I thought you distribute the 9 through (x+2)(x+1). and why is it (4x+4) instead of (4x-4) because -4 x 1 = -4 ....
Please help me learn how to foil correctly solving a quadratic equation.
(x+2)(x+1)=x²+3x+2
Multiply by 9:
9x²+27x+18
Now put it all together:
9x²+27x+18 -2x-2 -4x-4 = 0
group like terms:
9x²+21x+10=0
The next step is to factorize the expression by grouping:
Find m, n such that
m+n=21, m*n=90
so m=6, n=15
9x²+6x +15x+10 = 0
3x(3x+2) + 5(3x+2) =0
(3x+5)(3x+2)=0
So
x=-5/3 or x=-2/3