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The profit Rs y accumulated in thousand in x months is given by y = -x2 + 10x – 15. Find the best time to end the project. |
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Answer» y = -x2 + 10x – 15 ⇒ y = -[x2 – 10x + 52 – 52 + 15] ⇒ y = -[(x – 5)2 – 10] ⇒ y = 10 – (x – 5)2 ⇒ (x – 5)2 = -(y – 10) This is a parabola which is open downwards. Vertex is the maximum point. ∴ Profit is maximum when x – 5 = 0 (or) x = 5 months. After that profit gradually reduces. ∴ The best time to end the project is after 5 months. |
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