Pre calc vectors help. 1 question.

Question

Given vectors u= 7i+ 3j and v= –4i+ 3j, find 5u– 4v in terms of unit vectors i and j .

Answer 1

u = 7i + 3j and v = - 4i + 3j

Find 5u - 4v = ?

u = 7i + 3j

Multiply each side by 5.

5u = 5(7i + 3j) = 35i + 15j

v = - 4i + 3j

Multiply each side by 4.

4v = 4(- 4i + 3j) = - 16i + 12j

5u - 4v = (35i + 15j) - (-16i + 12j)

5u - 4v = (35i + 15j + 16i - 12j) = 51i + 3j

Hope it helps