8.在各项都为正数的等比数列{an}中,a1=3,前3项和为39,则公比q=( )
| A. | $\frac{1}{2}$ | B. | 2 | C. | 3 | D. | 4 |
6.过点A(-1,-2)且倾斜角为$\frac{π}{6}$的直线的参数方程为( )
| A. | $\left\{\begin{array}{l}{x=\frac{\sqrt{3}}{2}t-1}\\{y=\frac{t}{2}-2}\end{array}\right.$(t为参数) | B. | $\left\{\begin{array}{l}{x=\frac{\sqrt{3}}{2}t+1}\\{y=\frac{t}{2}+2}\end{array}\right.$(t为参数) | ||
| C. | $\left\{\begin{array}{l}{x=\frac{t}{2}+1}\\{y=\frac{\sqrt{3}}{2}t+2}\end{array}\right.$(t为参数) | D. | $\left\{\begin{array}{l}{x=\frac{t}{2}-1}\\{y=\frac{\sqrt{3}}{2}t-2}\end{array}\right.$ |
5.已知圆的参数方程$\left\{\begin{array}{l}{x=2cosθ+2}\\{y=2sinθ-1}\end{array}\right.$,则该圆的圆心为( )
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| A. | (-2,1) | B. | (2,-1) | C. | (2,1) | D. | (-2,-1) |