Question

PRE CAL

Let a = 2i + 9j, b = –4i + 5j, c = i – 3j, and d = 14j where i and j are unit vectors.

What is (a – b) – (2d – c) in terms of i and j?

5i – 27j
5i + 35j
7i – 27j
7i + 39j

Answer 1

C

Explanation:

EDGE

Answer 2

• 7i - 27j

Explanation:

Given

• a = 2i + 9j, b = –4i + 5j, c = i – 3j, d = 14j

To find

• (a – b) – (2d – c)

Solution

• (a – b) – (2d – c) =
• 2i + 9j - (–4i + 5j) - (2(14j) - (i – 3j)) =
• 2i + 9j + 4i - 5j - 28j + i - 3j =
• (2 + 4 + 1)i + (9 - 5 - 28 - 3)j =
• 7i + (-27)j =
• 7i - 27j