6.为了解某市20000名考生的毕业会考数学成绩,从中抽出100名考生的数学成绩进行调查,抽出的100名考生的数学成绩是( )
| A. | 总体 | B. | 样本 | C. | 个体 | D. | 样本容量 |
5.下列各方程组中,属于二元一次方程组的是( )
| A. | $\left\{{\begin{array}{l}{3x+2y=7}\\{xy=5}\end{array}}\right.$ | B. | $\left\{{\begin{array}{l}{2x+y=1}\\{x+z=2}\end{array}}\right.$ | C. | $\left\{{\begin{array}{l}{y=2x}\\{3x+4y=2}\end{array}}\right.$ | D. | $\left\{{\begin{array}{l}{\frac{5}{x}+\frac{y}{3}=\frac{1}{2}}\\{x+2y=3}\end{array}}\right.$ |
4.计算-3x2+4x2的结果为( )
| A. | -7x2 | B. | 7x2 | C. | -x2 | D. | x2 |
2.下列去括号中,正确的是( )
| A. | -(x-y+z)=-x+y-z | B. | x+2(y-z)=x+2y-z | ||
| C. | ${a^2}-\frac{3}{4}(a+2)={a^2}-\frac{3}{4}a+\frac{3}{2}$ | D. | a-(x-y+z)=a-x+y+z |
1.如图图形经过折叠,能围成正方体的是( )
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| A. | B. | C. | D. |