Answer:
-7 or 4
Step-by-step explanation:
use foil to get the quadratic equation:
x^2+5x-2x-10=18
x^2+3x-10=18
bring "18" to the left:
x^2+3x-10-18
x^2+3x-28
so what*what= -28
and
what+what=3
factors of -28: -7,4 -4,7 14,-2 -14,2 -28,1 -1,28
factors whose sum is 3: 7,-4
so substitute "7,-4" in place of 3:
x^2+7x-4x-28
2) split it in two groups
group 1) x^2+7x
group 2) -4x-28
x^2+7x has a GCF of "x"
x(x+7)
group 2) -4x-28 has a gcf of "-4"
-4(x+7)
3) (x-4) (x+7)=0
x-4=0
x=4
x+7=0
x=-7
x=4,-7
Hope this helps!
