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CIE 9231 2025 November Paper 14 Q7

A Level / CIE / FP1

CIE 9231 2025 Nov Paper 14 Paper · Question 7

题目

Problem

The curve CC has equation y=10x2−11x−1810x−18y=\dfrac{10x^2-11x-18}{10x-18}.

(a) Find the equations of the asymptotes of CC.

(3)

(b) Show that CC has no stationary points.

(4)

(c) Sketch CC, stating the coordinates of the points of intersection with the axes.

(3)

(d) Sketch the curve with equation y=∣10x2−11x−1810x−18∣y=\Big|\dfrac{10x^2-11x-18}{10x-18}\Big|.

(2)

(e) Given that ∣10x2−11x−1810x−18∣<4\Big|\dfrac{10x^2-11x-18}{10x-18}\Big|<4 for −29−444120<x<p\dfrac{-29-\sqrt{4441}}{20}<x<p and −29+444120<x<q\dfrac{-29+\sqrt{4441}}{20}<x<q, find the values of pp and qq.

(4)

题目中文翻译

曲线 CC 的方程为 y=10x2−11x−1810x−18y=\dfrac{10x^2-11x-18}{10x-18}。

(a) 求 CC 的渐近线方程。

(3)

(b) 证明 CC 没有驻点。

(4)

(c) 画出 CC 的草图,并写出曲线与坐标轴交点的坐标。

(3)

(d) 画出方程为 y=∣10x2−11x−1810x−18∣y=\Big|\dfrac{10x^2-11x-18}{10x-18}\Big| 的曲线的草图。

(2)

(e) 已知当 −29−444120<x<p\dfrac{-29-\sqrt{4441}}{20}<x<p 和 −29+444120<x<q\dfrac{-29+\sqrt{4441}}{20}<x<q 时,∣10x2−11x−1810x−18∣<4\Big|\dfrac{10x^2-11x-18}{10x-18}\Big|<4,求 pp 和 qq 的值。

(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

(a)

解法一

思路

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分母零点与分子不能约去。多项式除法给出斜渐近线,余项要写清楚。

答题过程

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Polynomial division gives

y=x+710−27/510x−18.y=x+\frac7{10}-\frac{27/5}{10x-18}.

At x=9/5x=9/5, the numerator is −27/5≠0-27/5\ne0, so the vertical asymptote is x=9/5\boxed{x=9/5}.

The remainder term tends to zero as ∣x∣→∞|x|\to\infty, giving the oblique asymptote y=x+7/10\boxed{y=x+7/10}.

(b)

解法一

思路

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对拆分后的函数求导,导数可直接写成1加正数,因此不可能为零。

答题过程

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Differentiating the expression in (a),

dydx=1+54(10x−18)2>0\frac{\mathrm{d}y}{\mathrm{d}x} =1+\frac{54}{(10x-18)^2}>0

for every x≠9/5x\ne9/5. Thus the derivative never vanishes on the domain, and C has no stationary points\boxed{C\text{ has no stationary points}}.

(c)

解法一

思路

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先因式分解分子求横轴交点,再用渐近线与严格递增性画两支。

答题过程

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The numerator factorises as

10x2−11x−18=(10x+9)(x−2).10x^2-11x-18=(10x+9)(x-2).

Hence the intercepts are (−9/10,0)\boxed{(-9/10,0)}, (2,0)\boxed{(2,0)} and (0,1)\boxed{(0,1)}.

Sketch two increasing branches with asymptotes x=9/5x=9/5 and y=x+7/10y=x+7/10. The left branch lies above the oblique asymptote, crosses the axes at (−9/10,0)(-9/10,0) and (0,1)(0,1), and tends to +∞+\infty as x→(9/5)−x\to(9/5)^-. The right branch lies below the oblique asymptote, starts from −∞-\infty as x→(9/5)+x\to(9/5)^+, crosses (2,0)(2,0) and increases towards the oblique asymptote.

(d)

解法一

思路

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反射函数值为负的两段,两个横轴交点都变成尖点,竖直渐近线仍要保留。

答题过程

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Reflect the parts with x<−9/10x<-9/10 and 9/5<x<29/5<x<2 in the xx-axis; keep the positive parts unchanged.

The graph lies on or above the xx-axis and has sharp minima at (−9/10,0)(-9/10,0) and (2,0)(2,0). It passes through (0,1)(0,1), tends to +∞+\infty on both sides of x=9/5x=9/5 and retains that vertical asymptote.

(e)

解法一

思路

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题目已给对应y=−4的两个边界,另外两个边界由y=4求出。用两支严格递增确认p、q的顺序。

答题过程

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The two stated lower endpoints come from y=−4y=-4. The upper endpoints satisfy y=4y=4:

10x2−11x−18= 4(10x−18),10x2−51x+54= 0,(2x−3)(5x−18)= 0.\begin{align*} 10x^2-11x-18=&\,4(10x-18), \\[4mm] 10x^2-51x+54=&\,0, \\[4mm] (2x-3)(5x-18)=&\,0. \end{align*}

Thus x=3/2x=3/2 or x=18/5x=18/5. Each branch of CC is strictly increasing. The root 3/23/2 lies to the left of the vertical asymptote 9/59/5 and is the upper endpoint of the first interval; 18/518/5 lies to its right and is the upper endpoint of the second interval.

Therefore p=3/2,q=18/5\boxed{p=3/2,\qquad q=18/5}.