Question

7．已知方程组$\left\{\begin{array}{l}{2x-y=7}\\{x+2y=-4}\end{array}\right.$的解是（　　）

• A． $\left\{\begin{array}{l}{x=-3}\\{y=2}\end{array}\right.$
• B． $\left\{\begin{array}{l}{x=2}\\{y=-3}\end{array}\right.$
• C． $\left\{\begin{array}{l}{x=1}\\{y=5}\end{array}\right.$
• D． $\left\{\begin{array}{l}{x=0}\\{y=-2}\end{array}\right.$

Answer 1

分析 方程组利用加减消元法求出解即可．

解答 解：$\left\{\begin{array}{l}{2x-y=7①}\\{x+2y=-4②}\end{array}\right.$，
①×2+②得：5x=10，即x=2，
把x=2代入①得：y=-3，
则方程组的解为$\left\{\begin{array}{l}{x=2}\\{y=-3}\end{array}\right.$，
故选B

点评 此题考查了解二元一次方程组，熟练掌握运算法则是解本题的关键．