七年级下学期数学练习题

完成时间：_______ 分钟     得分：_______

第一部分：实数

一、选择题（每题2分，共10分）

1. 下列各数中，是无理数的是（      ）。

A. $\sqrt{9}$     B. $\frac{3}{7}$     C. $0.1010010001\ldots$ (相邻两个1之间0的个数依次加1)     D. $3.\dot{1}4\dot{2}$

2. $\sqrt{64}$ 的算术平方根是（      ）。

A. 8     B. ±8     C. $2\sqrt{2}$     D. $2\sqrt[3]{8}$

3. 实数 $a$， $b$ 在数轴上的位置如图所示，则化简 $|a+b| - |a-b|$ 的结果是（      ）。

（注：此处为文字描述数轴位置：原点为O，点 $a$ 在原点左侧，且 $|a| > |b|$，点 $b$ 在原点右侧。）

A. $2a$     B. $2b$     C. $-2a$     D. $-2b$

4. 估计 $\sqrt{30}$ 的值在（      ）。

A. 3与4之间     B. 4与5之间     C. 5与6之间     D. 6与7之间

5. 下列说法正确的是（      ）。

A. 无限小数都是无理数     B. 带根号的数都是无理数

C. 实数包括正实数、零、负实数     D. 两个无理数的和一定是无理数

二、填空题（每空2分，共20分）

1. $-\sqrt[3]{27} =$ （      ）。

2. $\sqrt{5}-2$ 的相反数是（      ），绝对值是（      ）。

3. 比较大小：$-\pi$ （      ） $-3.14$； $\sqrt{15}$ （      ） 4（填“>”、“<”或“=”）。

4. 若 $\sqrt{a-3} + |b+5| = 0$，则 $a^b =$ （      ）。

5. 已知 $x$， $y$ 为实数，且 $y = \sqrt{x-4} + \sqrt{4-x} + 3$，则 $x^y =$ （      ）。

6. 一个正数的平方根是 $2a-1$ 和 $-a+2$，则这个正数是（      ）。

7. 计算：$(-\frac{1}{2})^{-2} - \sqrt{8} \times \sqrt{2} + (3-\pi)^0 =$ （      ）。

8. 若 $a$， $b$ 互为相反数，$c$， $d$ 互为倒数，$m$ 的绝对值是2，则 $\frac{a+b}{m} + m^2 - cd =$ （      ）。

三、计算题（每题5分，共20分）

1. $-\sqrt{\frac{49}{81}} + \sqrt{(-3)^2} - \sqrt[3]{-8}$

解：

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