Question

Find a • b. a = 4i + 3j, b = -4i + 4j

Answer 1

Hello,

I suppose a and b are vectors
and i and j unit's vectors

$\vec{i}*\vec{i}=1\\ \vec{j}*\vec{j}=1\\ \vec{i}*\vec{j}=0$
$\vec{a}\ .\ \vec{b}=(4\vec{i}\ +3 \vec{j}).(-4\vec{i}\ +4 \vec{j})\\ =-16-3*4*0+4*4*0+12=-4$