7.
如图,△ABC中,AB=5,BC=3,AC=4,以点C为圆心的圆与AB相切,则⊙C的半径为( )
| A. | 2.3 | B. | 2.4 | C. | 2.5 | D. | 2.6 |
5.如图,下列几何体的左视图不是矩形的是( )
| A. | B. | C. | D. |
18.植树节这天有20名同学共种了52棵树苗,其中男生每人种树3棵,女生每人种树2棵.设男生有x人,女生有y人,根据题意,下列方程组正确的是( )
0 305031 305039 305045 305049 305055 305057 305061 305067 305069 305075 305081 305085 305087 305091 305097 305099 305105 305109 305111 305115 305117 305121 305123 305125 305126 305127 305129 305130 305131 305133 305135 305139 305141 305145 305147 305151 305157 305159 305165 305169 305171 305175 305181 305187 305189 305195 305199 305201 305207 305211 305217 305225 366461
| A. | $\left\{\begin{array}{l}{x+y=52}\\{3x+2y=20}\end{array}\right.$ | B. | $\left\{\begin{array}{l}{x+y=52}\\{2x+3y=20}\end{array}\right.$ | C. | $\left\{\begin{array}{l}{x+y=20}\\{2x+3y=52}\end{array}\right.$ | D. | $\left\{\begin{array}{l}{x+y=20}\\{3x+2y=52}\end{array}\right.$ |