Multiplying a vector by a scalar means to multiply each coordinate of the vector by said scalar:
[tex]u = (-5, -9) \implies -8u = (40, 72)[/tex]
[tex]v = (6, 8) \implies 2v = (12, 16)[/tex]
Vectors are summed/subtracted by summing/subtracting correspondent coordinates:
[tex]-8u-2v = (40, 72) - (12, 16) = (40-12, 72-16) = (28, 56)[/tex]
