10.若关于x、y的方程组$\left\{\begin{array}{l}x+2y=5\\ 2x+ay=4\end{array}\right.$的解都是正整数,那么整数a的值有( )
| A. | 1个 | B. | 2个 | C. | 3个 | D. | 4个 |
9.已知α、β互余,且α比β大30°.则下列方程组中符合题意的是( )
| A. | $\left\{\begin{array}{l}α+β=180\\ α=β-30\end{array}\right.$ | B. | $\left\{\begin{array}{l}α+β=180\\ α=β+30\end{array}\right.$ | C. | $\left\{\begin{array}{l}α+β=90\\ α=β+30\end{array}\right.$ | D. | $\left\{\begin{array}{l}α+β=90\\ α=β-30\end{array}\right.$ |
8.若多项式a2+kab+b2是完全平方式,则常数k的值为( )
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| A. | 2 | B. | 4 | C. | ±2 | D. | ±4 |