9.
如图,已知AB∥CD,那么下列结论中正确的是( )
| A. | ∠3=∠4 | B. | ∠1=∠2 | C. | ∠2=∠3 | D. | ∠1+∠ACD=180° |
8.化简:
(1)$\frac{1}{{2+\sqrt{3}}}$;
(2)$10\sqrt{\frac{1}{5}}+\frac{5}{2}\sqrt{\frac{4}{5}}-\sqrt{45}$.
(1)$\frac{1}{{2+\sqrt{3}}}$;
(2)$10\sqrt{\frac{1}{5}}+\frac{5}{2}\sqrt{\frac{4}{5}}-\sqrt{45}$.
4.已知二元一次方程组$\left\{\begin{array}{l}{ax+3y=9}\\{2x-3y=-4}\end{array}\right.$的解,也是二元一次方程6x+y=8的解,求a的值.
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