Question

18．方程組$\left\{\begin{array}{l}{x-2y=9}\\{3x+2y=-1}\end{array}\right.$的解是$\left\{\begin{array}{l}{x=2}\\{y=-\frac{7}{2}}\end{array}\right.$．

Answer 1

分析 方程組利用加減消元法求出解即可．

解答 解：$\left\{\begin{array}{l}{x-2y=9①}\\{3x+2y=-1②}\end{array}\right.$，
①+②得：4x=8，即x=2，
把x=2代入①得：y=-$\frac{7}{2}$，
則方程組的解為$\left\{\begin{array}{l}{x=2}\\{y=-\frac{7}{2}}\end{array}\right.$．
故答案為：$\left\{\begin{array}{l}{x=2}\\{y=-\frac{7}{2}}\end{array}\right.$

點(diǎn)評(píng) 此題考查了解二元一次方程組，利用了消元的思想，消元的方法有：代入消元法與加減消元法．