SOLUTION: How do you multiply expressions, using variables, within a set of parentheses? the problem I'm working on: (X+3) (4x+5) sorry if this is a super obvious one, I'm still in Al

Question 819671: How do you multiply expressions, using variables, within a set of parentheses?
the problem I'm working on:
(X+3) (4x+5)
sorry if this is a super obvious one, I'm still in Algebra 1. :P
Answer by richwmiller(17219) (Show Source): You can put this solution on YOUR website!
Be careful X is not the same as x.
(X+3) (4x+5)
I will assume you really meant
(x+3) (4x+5)
The method is called FOIL.
First x+4x which equals 4x^2
outer x*5
inner 3*4x
last 3*5
add them
4x^2+5x+12x_+15
4x^2+17x+15
We are finished.
but to work backwards
we want factors of 60 (4*15) which add up to 17
5*12=60 5+12=17
4x^2+5x+12x_+15
4x^2+12x+5x+15
4x*(x+3)+5*(x+3)
(4x+5)*(x+3)
and we are back where we started.

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