满足方程组{2x+y=a 4x+3y=-a-8}的x,y的值的和等于3a,则a=____急急急

问题描述:

满足方程组{2x+y=a 4x+3y=-a-8}的x,y的值的和等于3a,则a=____急急急

2x+y=a
4x+3y=-a-8
6x+3y=3a
2x=4a+8
x=2a+4
2(2a+4)+y=a
y=-3a-8
2a+4-3a-8=3a
2a-3a-3a=8-4
-3a=4
a=-4/3