You have to FOIL (multiply the first, then outer, then inner, then last)
(x-2)(x+4)
First: multiply x by x to get x².
Outer: multiply x by 4 to get 4x.
Inner: multiply -2 by x to get -2x.
Last: multiply -2 by 4 to get -8.
This gives you:
x² + 4x - 2x - 8
Combine like terms to get your final answer:
x² + 2x - 8
Hope this helped!! xx