当a=______时,方程组x+2y-6=0,且x-y-9+3a=0的解满足x=y.

题目

当a=______时,方程组x+2y-6=0,且x-y-9+3a=0的解满足x=y.

答案

把x=y 带入原式,可得a=3.或者两个方程合并化简得y=a-1,x=8-2a,若x=y,也可得a=3