Question

19．請寫出一個(gè)二元一次方程組$\left\{\begin{array}{l}{x+y=0}\\{x-y=-2}\end{array}\right.$，使它的解是$\left\{\begin{array}{l}{x=-1}\\{y=1}\end{array}\right.$．

Answer 1

分析 由x=-1，y=1為解列出方程組即可．

解答 解：$\left\{\begin{array}{l}{x+y=0}\\{x-y=-2}\end{array}\right.$的解為$\left\{\begin{array}{l}{x=-1}\\{y=1}\end{array}\right.$．
故答案為：$\left\{\begin{array}{l}{x+y=0}\\{x-y=-2}\end{array}\right.$．

點(diǎn)評 此題考查了二元一次方程組的解，方程組的解即為能使方程值域中兩方程成立的未知數(shù)的值．