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If the points A (1, 2), B (0, 0) and C (a, b) are collinear, then A. a = b B. a = 2b C. 2a = b D. a = - b |
Answer» Let the points are; A = (x1, y1) = (1, 2) B = (x2, y2) = (0, 0) C = (x3, y3) = (a, b) ∵ Area of ∆ABC= ∆ = 1/2 [x1(y2 – y3) + x2(y3 – y1) + x3(y1 – y2)] ∴ ∆ =1/2 [1(0 - b) + 0(b - 2) + a(2 - 0)] ⇒Δ=1/2 ( - b + 0 + 2a)=1/2(2a - b) As, the points A (1, 2), B (0, 0) and C (a, b) are collinear, then area of ΔABC will be equals to the zero Area of ΔABC = 0 ⇒1/2 (2a - b) → 2a - b = 0 → 2a = b Hence, the required relation is 2a = b |
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