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Passage: For the parabola y2 = 4ax, the vertex is (0, 0), the focus is (a, 0) and the directrix is x + a = 0. Answer the following three questions.(i) The vertex of the parabola (y - 1)2 = 2(x - 1) is (A) (1,0)(B) (2,0) (C) (1,1)(D) (0,1)(ii) Focus of the parabola y2 = 4(x - 1) is(A) (1, 0)(B) (2, 0)(C) (1, 1)(D) (2, 2)(iii) The directrix of the parabola (y - 2)2 = 4(x - 1)(A) x = 1(B) x = -1(C) x = 2 (D) x = 0 |
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Answer» Correct option (i)(c)(ii)(b)(iii)(d) Explanation : (i) The parabola is Y2 = 4(1/2)(x) where X = x - 1 and Y = y - 1. Therefore, the vertex is (X = 0, Y = 0) = (x - 1 = 0, y - 1 = 0) = (1, 1) (ii) y2 = 4(x -1) is Y2 = 4X where X = x - 1 and Y = y and a - 1. The focus is (X = 1, Y = 0) =(x - 1 = 1,y = 0) = (2,0) (iii) (y - 2)2 = 4(x - 1) ⇒ Y2 = 4X where X = x - 1 and Y = y − 2. The directrix equation is X = -a = -1 ⇒ x - 1 = -1 ⇒ x = 0 |
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