Question

16．方程組$\left\{\begin{array}{l}{x+y=1}\\{2y-x=8}\end{array}\right.$的解是（　�。�

• A． $\left\{\begin{array}{l}{x=-2}\\{y=3}\end{array}\right.$
• B． $\left\{\begin{array}{l}{x=2}\\{y=-3}\end{array}\right.$
• C． $\left\{\begin{array}{l}{x=4}\\{y=-3}\end{array}\right.$
• D． $\left\{\begin{array}{l}{x=-3}\\{y=4}\end{array}\right.$

Answer 1

分析 ①+②得出3y=9，求出y=3，把y=3代入①得出x+3=1，求出x即可．

解答 解：$\left\{\begin{array}{l}{x+y=1①}\\{2y-x=8②}\end{array}\right.$
①+②得：3y=9，
解得：y=3，
把y=3代入①得：x+3=1，
解得：x=-2，
所以原方程組的解為$\left\{\begin{array}{l}{x=-2}\\{y=3}\end{array}\right.$，
故選A．

點(diǎn)評(píng) 本題考查了解二元一次方程組和解一元一次方程的應(yīng)用，解此題的關(guān)鍵是能把二元一次方程組轉(zhuǎn)化成一元一次方程，難度不是很大．