For which λ are λ i + 2 j + k and 4 i - 9 j + 2 k perpendicular?

Vectors · Question 74 of 125

Question 74

MediumOriginal question

For which $\lambda$ are $\lambda\hat{i} + 2\hat{j} + \hat{k}$ and $4\hat{i} - 9\hat{j} + 2\hat{k}$ perpendicular?

-4

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4

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\frac{9}{2}

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5

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Show the answer and explanation

CorrectNot quiteAnswer B

Correct answer: B

Worth noting

$\frac{9}{2}$ leaves out the $\hat{k}$ term, $1 \times 2$ .

Ten questions from Vectors, at your own pace.

Ten questions from Vectors, at your own pace.