WAEC - Further Mathematics (2024 - No. 14)

If r = i + 2j and n = -i + 3j, find |2n - r|.
3.6
4.0
5.0
8.5

Explanation

Given that, r = i + 2j and n = -i + 3j, to find |2n - r|

2n = 2(- i + 3j) = - 2i + 6j

2n - r = [- 2i + 6j] - [ i + 2j] = -3i + 4j

|2n - r| = |-3i + 4j| = \(\sqrt{(-3)^2 + 4^2}\) = \(\sqrt{9 + 16}\) = \(\sqrt{25}\) = 5.0

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