let u=-7i+3j and v=2i-j. Find ||u+v||^2 -||u-v||^2 Solution Answer: u+v=-7i+3j+2i-j u+v=-5i+2j |u+v|=[(-5) 2 +(2) 2 ] |u+v|=29 ||u+v||^2=29 u-v=-7i+3j-(2i-j) u-v=-7i+3j-2i+j u-v=-9i+4j |u-v|=[(-9) 2 +(4) 2 ] |u-v|=97 ||u-v||^2=97 ||u+v||^2 -||u-v||^2=29-97 ||u+v||^2 -||u-v||^2=-68 .