When do you FOIL?

Answer 1

In math, you FOIL when multiplying two binomials. Really, FOIL is just the distributive property; it's just a rule to help make sure you multiply everything in the first binomial by everything in the second. So (x+1)(x+3) is an example of this. It is done by multiplying the first terms, outside terms, inside terms, and then last terms. This is x2+3x+x+3. Simplified, this is x2+4x+3.