Hi, F First terms O Outside terms I Inside terms L Last terms a.) (x + √y)(x - √y) = x^2 + y ||Note: x^2 designates x squared b.) (2 - √3)(2 + √3) = 4 - 3 = 1 c.) (√6 + √2)( √6 - √2) = 6-2 = 4 d.) (4 - √5)(4 + √5) = 16 - 5 = 11