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If 2x + y + k = 0 is a normal to the parabola y2 = − 8x, then the value of k is(A) 12(B) 24(C) − 12(D) − 24 |
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Answer» Correct option (B) 24 Explanation : Suppose 2x + y + k = 0 is normal at (-2t2, -4t). However, the normal at (-2t2, -4t) is tx + y = -4t - 2t3 ⇒ tx + y + 4t + 2t3 = 0 Therefore t/2 = 1/1 = 4t + 2t3/k ⇒ t = 2 and k = 24 |
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