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IAL 2021 Oct Q3

A Level / Edexcel / P4

IAL 2021 Oct Paper · Question 3

题目

Problem

g(x)=3x3+8x23x6x(x+3)Ax+B+Cx+Dx+3g(x)=\frac{3x^3+8x^2-3x-6}{x(x+3)}\equiv Ax+B+\frac{C}{x}+\frac{D}{x+3}

(a) Find the values of the constants AA, BB, CC and DD.

(5)

A curve has equation

y=g(x)x>0y=g(x)\qquad x>0

Using the answer to part (a),

(b) find g(x)g'(x).

(2)

(c) Hence, explain why g(x)>3g'(x)>3 for all values of xx in the domain of gg.

(1)
题目中文翻译 g(x)=3x3+8x23x6x(x+3)Ax+B+Cx+Dx+3g(x)=\frac{3x^3+8x^2-3x-6}{x(x+3)}\equiv Ax+B+\frac{C}{x}+\frac{D}{x+3}

(a) 求常数 A,B,C,DA,B,C,D 的值。

曲线的方程为

y=g(x)x>0y=g(x)\qquad x>0

利用第 (a) 问的答案,

(b) 求 g(x)g'(x)

(c) 进而说明为什么对于 gg 的定义域内所有 xx 的值,都有 g(x)>3g'(x)>3

解答