Question

Sabendo que IuI = 3, IvI = 7 e u*v= -2, calcule:A) (3u+2v)*(u-v)

Answer 1

$(3u+v)(u-v)=3 u^2-u v-2 v^2\\ \\ |u|=3\Rightarrow u^2=9\\ |v|=7\Rightarrow v^2=49\\ uv=-2\\ \\ Substituindo:\\ \\ 3 u^2-u v-2 v^2=3*9-(-2)-2*49=27+2-98=-69$