Question

12．方程组$\left\{\begin{array}{l}{2x-y=1}\\{2x-3y=5}\end{array}\right.$的解是（　　）

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

Answer 1

分析 方程组利用加减消元法求出解即可．

解答 解：$\left\{\begin{array}{l}{2x-y=1①}\\{2x-3y=5②}\end{array}\right.$，
①-②得：2y=-4，即y=-2，
把y=-2代入①得：x=-$\frac{1}{2}$，
则方程组的解为$\left\{\begin{array}{l}{x=-\frac{1}{2}}\\{y=-2}\end{array}\right.$，
故选D

点评 此题考查了解二元一次方程组，利用了消元的思想，消元的方法有：代入消元法与加减消元法．