7.以方程组$\left\{\begin{array}{l}{2x+y=t-1}\\{x-y=2t+7}\end{array}\right.$ 的解x、y分别作为某个点的横、纵坐标,得到一个点(x,y),若点(x,y)在第四象限,则t的取值范围是( )
| A. | -5<t<-2 | B. | t>-2 | C. | -2<t<5 | D. | t>-5 |
2.二次根式$\sqrt{{a}^{2}+{b}^{2}}$,$\sqrt{2{b}^{3}}$,$\sqrt{\frac{a}{2}}$,4$\sqrt{3a}$,$\sqrt{8}$,$\sqrt{0.2}$中,最简二次根式有( )
0 297018 297026 297032 297036 297042 297044 297048 297054 297056 297062 297068 297072 297074 297078 297084 297086 297092 297096 297098 297102 297104 297108 297110 297112 297113 297114 297116 297117 297118 297120 297122 297126 297128 297132 297134 297138 297144 297146 297152 297156 297158 297162 297168 297174 297176 297182 297186 297188 297194 297198 297204 297212 366461
| A. | 1个 | B. | 2个 | C. | 3个 | D. | 4个 |