##(x+h)(x+h) = F + O + I + L##
##= (x*x) + (x*h) + (h*x) + (h*h)##
##=x^2 + 2hx + h^2##
FOIL is a useful mnemonic to help you remember all the combinations to multiply when multiplying two binomials.
In addition, if the binomials are both in standard order, then FOIL tends to group the terms in a helpful way.
To multiply ##(x+h)(x+h)## add together each of the products:
First : ##x*x = x^2##
Outside : ##x*h = hx##
Inside: ##h*x = hx##
Last: ##h*h = h^2##
Added together:
##x^2+hx+hx+h^2 = x^2+2hx+h^2##
