Question

5．方程組$\left\{\begin{array}{l}{x+y=1}\\{3x-y=-5}\end{array}\right.$的解為（　�。�

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

Answer 1

分析 根據(jù)加減法，可得方程組的解．

解答 解：兩式相加，得4x=-4，
解得x=-1．
把x=-1代入x+y=1，得
y=2，
方程組的解為$\left\{\begin{array}{l}{x=-1}\\{y=2}\end{array}\right.$，
故選：B．

點評 本題考查了二元一次方程組的解，利用加減法是解題關(guān)鍵．