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The value of k such that the line (x - 4)/1 = (y - 2)/1 = (z - k)/2 lies in the plane 2x - 4y + z - 7 = 0 is(A) 7 (B) −7 (C) no real value (D) 4 |
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Answer» Correct option is (A) 7 Explanation : Every point on the given line is of the form (4 + λ, 2 + λ, k + 2λ), where λ ∈ R. This point lies in the plane 2x - 4y + z - 7 = 0 So 2(4 + λ) - 4(2 + λ) + l(k + 2λ) - 7 = 0 for all λ ∈ R In particular, for λ = 0, we have 8 - 8 + k - 7 = 0 k = 7 Note that the point (4, 2, k) lies on the given line and hence it lies in the given plane. So 2(4) - 4(2) + k - 7 = 0 k = 7 |
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