Help-me-Please

If a = 3i + 2j and b=-2i+j calculate |a+b| a and b are vectors and i and j have the arrow pointy thing above it instead of the dots. The correct answer is square root 11. So, what I did was substitute a + b with the equations: =(3i+2j-k)+(-2i+j) =i+3j-k N...

The textbook answer is -80 Question: find (3a+4b)(2b+4a) if a= -i-3j+k and b=2i+4j-5k What I did: =6(a)(b) - 12|a|^2 + 2|b|^2 - 4(a)(b) =2(a)(b)-12|a|^2+2|b|^2 substitute a and b with given equations. Added like terms for each part.(too long to write out)...