《2025年赢在暑假抢分计划七年级数学人教版》

例1 (无锡)二元一次方程组$\left\{\begin{array}{l} 3x+2y= 12①,\\ 2x-y= 1②\end{array} \right. $的解为$\begin{cases}x = 2\\y = 3\end{cases}$.
剖析:由②,得$y= 2x-1$③.将③代入①,得$3x+2(2x-1)= 12$,解得$x= 2$.将$x= 2$代入③,得$y= 3$.∴原方程组的解为$\left\{\begin{array}{l} x= 2,\\ y= 3.\end{array} \right. $
解答:$\left\{\begin{array}{l} x= 2,\\ y= 3\end{array} \right. $

答案： $\begin{cases}x = 2\\y = 3\end{cases}$

例2 (济南)方程组$\left\{\begin{array}{l} x+y= 5,\\ 2x+5y= 28\end{array} \right. $的解是(C)
A.$\left\{\begin{array}{l} x= 2,\\ y= 3\end{array} \right. $
B.$\left\{\begin{array}{l} x= -1,\\ y= -6\end{array} \right. $
C.$\left\{\begin{array}{l} x= -1,\\ y= 6\end{array} \right. $
D.$\left\{\begin{array}{l} x= -2,\\ y= -3\end{array} \right. $

答案： C