Using FOIL (First, Outer, Inner, Last):
(x+3)(x-4)
FIRST: multiply x times x to get x^2.
OUTER: multiply x times -4 to get -4x.
INNER: multiply 3 times x to get 3x.
LAST: multiply 3 times -4 to get -12.
Your expression now looks like:
x^2-4x+3x-12
Combine like terms.
x^2-x-12
The answer is D. x^2-x-12.
I hope this helps :)
