1.已知不等式组$\left\{\begin{array}{l}{x>a}\\{x≥1}\end{array}\right.$的解集是x≥1,则a的取值范围是( )
| A. | a<1 | B. | a≤1 | C. | a≥1 | D. | a>1 |
20.已知直线l1:y=-3x+b与直线l2:y=-kx+1在同一坐标系中的图象交于点(1,-2),那么方程组$\left\{\begin{array}{l}{3x+y=b}\\{kx+y=1}\end{array}\right.$的解是( )
| A. | $\left\{\begin{array}{l}{x=1}\\{y=-2}\end{array}\right.$ | B. | $\left\{\begin{array}{l}{x=1}\\{y=2}\end{array}\right.$ | C. | $\left\{\begin{array}{l}{x=-1}\\{y=-2}\end{array}\right.$ | D. | $\left\{\begin{array}{l}{x=-1}\\{y=2}\end{array}\right.$ |
19.设抛物线C1:y=x2向右平移2个单位长度,再向下平移3个单位长度得到抛物线C2,则抛物线C2对应的函数解析式是( )
| A. | y=(x-2)2-3 | B. | y=(x+2)2-3 | C. | y=(x-2)2+3 | D. | y=(x+2)2+3 |
18.当x=6,y=-2时,代数式$\frac{{x}^{2}-{y}^{2}}{(x-y)^{2}}$的值为( )
| A. | 2 | B. | $\frac{4}{3}$ | C. | 1 | D. | $\frac{1}{2}$ |
17.一种饮料有两种包装,5大盒、4小盒共装148瓶,2大盒、5小盒共装100瓶,大盒与小盒每盒各装多少瓶?设大盒装x瓶,小盒装y瓶,则可列方程组( )
0 285658 285666 285672 285676 285682 285684 285688 285694 285696 285702 285708 285712 285714 285718 285724 285726 285732 285736 285738 285742 285744 285748 285750 285752 285753 285754 285756 285757 285758 285760 285762 285766 285768 285772 285774 285778 285784 285786 285792 285796 285798 285802 285808 285814 285816 285822 285826 285828 285834 285838 285844 285852 366461
| A. | $\left\{\begin{array}{l}{5x+4y=148}\\{2x+5y=100}\end{array}\right.$ | B. | $\left\{\begin{array}{l}{4x+5y=148}\\{2x+5y=100}\end{array}\right.$ | ||
| C. | $\left\{\begin{array}{l}{5x+4y=148}\\{5x+2y=100}\end{array}\right.$ | D. | $\left\{\begin{array}{l}{4x+5y=148}\\{5x+2y=100}\end{array}\right.$ |