Question

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

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

Answer 1

分析 方程组利用加减消元法求出解即可．

解答 解：$\left\{\begin{array}{l}{2x-y=3①}\\{x+3y=5②}\end{array}\right.$，
①×3+②得：7x=14，即x=2，
把x=2代入②得：y=1，
则方程组的解为$\left\{\begin{array}{l}{x=2}\\{y=1}\end{array}\right.$．
故选C．

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．