Question 48

Mathematics Scalar and Vector Products Hard

The value of non-zero scalars&nbsp;&alpha; and&nbsp;&beta; for all vectors&nbsp;<span class="math-tex">\(\vec a\)</span>&nbsp;and&nbsp;<span class="math-tex">\(\vec b\)</span>,&nbsp;such that&nbsp;<span class="math-tex">\(\rm \alpha\left(2\vec a-\vec b \right)+\beta\left(\vec a + 2\vec b\right)=8\vec b - \vec a \)</span>&nbsp;is:

(A) &alpha; = 2,&nbsp;&beta; = 1
(B) &alpha; = -2,&nbsp;&beta; = -3
(C) &alpha; = 1,&nbsp;&beta; = 3
(D) &alpha; = -2,&nbsp;&beta; = 3
✓ Correct Answer: Option D Verified Solution

📘 Step-by-Step Solution & Detailed Explanation:

Compare the coefficients of \(\vec{a}\) and \(\vec{b}\) (they can be any vectors):

  • \(\vec{a}\): \(2\alpha + \beta = -1\)
  • \(\vec{b}\): \(-\alpha + 2\beta = 8\)

From the first, \(\beta = -1 - 2\alpha\). Substitute: \(-\alpha - 2 - 4\alpha = 8 \Rightarrow \alpha = -2\), then \(\beta = 3\).

Answer: (D) α = −2, β = 3

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