5) (-√3+√2)(1+√2) = -√3-√3*√2+√2+√2*√2 = -√3-√6+√2+2
6) (√3-√15)(1+√5) = √3+√3*√5-√15-√75 = √3+√15-√15-5√3 = -4√3
7) (2√3-√2)(3-√2) = 3*2√3-2√3*√2-3√2+√2*√2 = 6√3-2√6-3√2+2
