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1. 解方程组$\left\{\begin{array}{l} 3m - 4n = 7,\\ 9m - 10n + 25 = 0\end{array}\right. $①②的最好方法是(C)
A. 由①得$m = \frac{7 + 4n}{3}$，再代入②
B. 由②得$m = \frac{10n - 25}{9}$，再代入①
C. 由①得$3m = 4n + 7$，再代入②
D. 由②得$9m = 10n - 25$，再代入①

答案： C

2. 方程组$\left\{\begin{array}{l} 3x + 5y = 25,\\ 4x + 3y = 15\end{array}\right. $的解满足方程$2x - ky = 10$，则$k$的值是(A)
A. $-2$
B. $-1$
C. $0$
D. $5$

答案： A

3. 设$y = kx + b$，当$x = 1$时，$y = 1$；当$x = 2$时，$y = -4$，则$k$和$b$的值分别为(C)
A. $\left\{\begin{array}{l} k = 3,\\ b = -2\end{array}\right. $
B. $\left\{\begin{array}{l} k = -3,\\ b = 4\end{array}\right. $
C. $\left\{\begin{array}{l} k = -5,\\ b = 6\end{array}\right. $
D. $\left\{\begin{array}{l} k = 6,\\ b = -5\end{array}\right. $

答案： C

4. 长江比黄河长$923$km，黄河长度的$6$倍比长江长度的$5$倍多$849$km，设长江、黄河的长度分别为$x$km，$y$km，则下列方程组中正确的是(B)
A. $\left\{\begin{array}{l} x - y = 923,\\ 5x - 6y = 849\end{array}\right. $
B. $\left\{\begin{array}{l} x - y = 923,\\ 6y - 5x = 849\end{array}\right. $
C. $\left\{\begin{array}{l} y - x = 923,\\ 6y - 5x = 849\end{array}\right. $
D. $\left\{\begin{array}{l} y - x = 923,\\ 5x - 6y = 849\end{array}\right. $

答案： B

5. 一张试卷有25道题，做对一题得4分，做错一题倒扣1分. 小明做了全部试题得70分，则他做对的题数是(D)
A. $16$道
B. $17$道
C. $18$道
D. $19$道

答案： D

1. 方程组$\left\{\begin{array}{l} x + 2y = 4,\\ x + y = 1\end{array}\right. $的解为$\left\{\begin{array}{l} x=-2,\\ y=3\end{array}\right. $.

答案： $\left\{\begin{array}{l} x=-2,\\ y=3\end{array}\right. $

2. 方程$\frac{2x - y}{5} = \frac{x + y}{3} = 3$的解为$\left\{\begin{array}{l} x=8,\\ y=1\end{array}\right. $.

答案： $\left\{\begin{array}{l} x=8,\\ y=1\end{array}\right. $

3. 二元一次方程组$\left\{\begin{array}{l} 9x + 4y = 1,\\ x + 6y = -11\end{array}\right. $的解满足$2x - ky = 10$，则$k = $4.

答案： 4

4. 已知$(3x + 2y - 5)^2$与$|5x + 3y - 8|$互为相反数，则$x = $1，$y = $1.

答案： 1,1

5. 在方程$y = kx + b$中，若$x = 5$时，$y = 6$；$x = -1$时，$y = -2$. 则当$x = 2$时，$y = $2.

答案： 2

1. 已知$\frac{2x + y}{2} = \frac{5x + 2y}{4} = 1$，求$\frac{x + 2y + 1}{2x - 3y + 7}$的值.5

答案： 5