find the following product:(x-3)(x+3)
you could use FOIL or the distributive property but I see instantly that this is the factors of the difference of two squares:
a^2-b^2 = (a-b)(a+b)
so the answer by inspection is:
x^2-9
a^2-b^2 = (a-b)(a+b)
so the answer by inspection is:
x^2-9