The FOIL method is a useful way to recall how to expand the product of two binomials (a+b)x(c+ d). Multiply the First terms, Outer terms, Inner terms, and the Last terms of the binomials, and sum the four products to obtain the formula (a+b)x(c+d)= ac+ ad+bc+ bd. Explain how the rectangular area diagram shown to the right justifies the FOIL method. a + b What is the area of F? The area of F is F 0 L C + d