In multiplying two binomials we just perform FOIL method, it is simply like distribution so for example:
(x+1)(x+2) we do First, Outer, Inner, Last
First: (x+1)(x+2) : x²
Outer: (x+1)(x+2) : 2x
Inner: (x+1)(x+2) : x
Last: (x+1)(x+2) : 2
We add all so:
(x+1)(x+2)
= x²+2x+x+2
= x²+3x+2
