Question

20．方程組$\left\{\begin{array}{l}2x+y=4\\ 2x-y=0\end{array}\right.$的解是（　�。�

• A． $\left\{\begin{array}{l}x=-1\\ y=2\end{array}\right.$
• B． $\left\{\begin{array}{l}x=1\\ y=2\end{array}\right.$
• 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 方程組利用加減消元法求出解即可．

解答 解：$\left\{\begin{array}{l}{2x+y=4①}\\{2x-y=0②}\end{array}\right.$，
①+②得：4x=4，即x=1，
把x=1代入①得：y=2，
則方程組的解為$\left\{\begin{array}{l}{x=1}\\{y=2}\end{array}\right.$，
故選B

點評 此題考查了解二元一次方程組，熟練掌握運算法則是解本題的關(guān)鍵．