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CIE 9709 2022 June Paper 12 Q3

A Level / CIE / P1

CIE 9709 2022 June Paper 12 Paper · Question 3

题目

Problem

The equation of a curve is such that dydx=3(4x−7)12−4x−12\frac{\mathrm{d}y}{\mathrm{d}x}=3(4x-7)^{\frac12}-4x^{-\frac12}. It is given that the curve passes through the point (4,52)\big(4,\frac52\big).

Find the equation of the curve.

(4)
题目中文翻译

一条曲线的方程满足 dydx=3(4x−7)12−4x−12\frac{\mathrm{d}y}{\mathrm{d}x}=3(4x-7)^{\frac12}-4x^{-\frac12}。已知曲线经过点 (4,52)\big(4,\frac52\big)。

求曲线的方程。

(4)
原卷通用作答要求

Answer all questions. You should use a calculator where appropriate.

You must show all necessary working clearly; no marks will be given for unsupported answers from a calculator.

Give non-exact numerical answers correct to 3 significant figures, or 1 decimal place for angles in degrees, unless a different level of accuracy is specified in the question.

请回答所有题目。适当时应使用计算器。必须清楚展示所有必要的计算过程;仅给出计算器答案而没有过程,不予评分。除非题目另有精度要求,非精确数值答案保留 3 位有效数字,以度为单位的角度保留 1 位小数。

解答

解法一

思路

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对括号幂积分时要除以括号内的斜率。再用给定点确定积分常数。

答题过程

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Integrating the two terms gives

y=12(4x−7)3/2−8x+C.y=\frac12(4x-7)^{3/2}-8\sqrt x+C.

At x=4x=4, the first two terms sum to 27/2−16=−5/227/2-16=-5/2. The given height is 5/25/2, so C=5C=5. Hence y=12(4x−7)3/2−8x+5y=\tfrac12(4x-7)^{3/2}-8\sqrt x+5.