How do I expand a factorised expression?

Take example (x+3)(x-4) We use FOIL - first, outer, inner, last  We multiply each part by the other part. First -> x times x = x² . Outer -> x times -4 = -4x (remember the minus infront of the 4), Inner -> 3 times x  = 3x. Last - -4 times 3 = -12 (again, remember minus infront of the 4) We then add the four answers from FOIL together: x²-4x+3x-12 From here we can simplify: x²-x-12