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CIE 9231 2025 June Paper 44 Q4

A Level / CIE / FS

CIE 9231 2025 June Paper 44 Paper · Question 4

题目

Problem

The continuous random variable XX has probability density function ff given by

f(x)={kx,0x<1,kx2,1x2,0,otherwise.f(x)= \begin{cases} kx, & 0 \leq x < 1,\\ kx^2, & 1 \leq x \leq 2,\\ 0, & \text{otherwise}. \end{cases}

(a) Show that k=617k=\frac{6}{17}.

[2]

(b) Find the cumulative distribution function of XX.

[3]

(c) Find the median value of XX.

[2]

(d) Find E(1X)E\bigl(\frac{1}{X}\bigr).

[2]
题目中文翻译

连续随机变量 XX 的概率密度函数 ff

f(x)={kx,0x<1,kx2,1x2,0,otherwise.f(x)= \begin{cases} kx, & 0 \leq x < 1,\\ kx^2, & 1 \leq x \leq 2,\\ 0, & \text{otherwise}. \end{cases}

(a) 证明 k=617k=\frac{6}{17}

(b)XX 的累积分布函数。

(c)XX 的中位数。

(d)E(1X)E\bigl(\frac{1}{X}\bigr)

解答