Question

6．解为$\left\{\begin{array}{l}{x=4}\\{y=8}\end{array}\right.$的方程组是（　　）

• A． $\left\{\begin{array}{l}{x+y=2}\\{x-y=1}\end{array}\right.$
• B． $\left\{\begin{array}{l}{2x-y=0}\\{x+y=12}\end{array}\right.$
• C． $\left\{\begin{array}{l}{3x+2y=13}\\{x-3y=-3}\end{array}\right.$
• D． $\left\{\begin{array}{l}{3x-2y=4}\\{3x+2y=8}\end{array}\right.$

Answer 1

分析 只要把$\left\{\begin{array}{l}{x=4}\\{y=8}\end{array}\right.$代入方程组的每一个方程，看看两边是否相等即可．

解答 解：A、把$\left\{\begin{array}{l}{x=4}\\{y=8}\end{array}\right.$代入方程组$\left\{\begin{array}{l}{x+y=2}\\{x-y=1}\end{array}\right.$，两个方程的左边和右边都不相等，故不是此方程组的解，故本选项错误；
B、把$\left\{\begin{array}{l}{x=4}\\{y=8}\end{array}\right.$代入方程组$\left\{\begin{array}{l}{2x-y=0}\\{x+y=12}\end{array}\right.$，两个方程的左边和右边都相等，故是此方程组的解，故本选项正确；
C、把$\left\{\begin{array}{l}{x=4}\\{y=8}\end{array}\right.$代入方程组$\left\{\begin{array}{l}{3x+2y=13}\\{x-3y=-3}\end{array}\right.$，两个方程的左边和右边都不相等，故不是此方程组的解，故本选项错误；
D、把$\left\{\begin{array}{l}{x=4}\\{y=8}\end{array}\right.$代入方程组$\left\{\begin{array}{l}{3x-2y=4}\\{3x+2y=8}\end{array}\right.$，两个方程的左边和右边都不相等，故不是此方程组的解，故选项错误；
故选B．

点评 本题考查了二元一次方程组的解的应用，能理解二次一次方程组的解的定义是解此题的关键．