已知方程组{2x+y=2a,x+2y=1-5a},若x+y的值为非负数,求a的取值范围.急用,急急急····························
问题描述:
已知方程组{2x+y=2a,x+2y=1-5a},若x+y的值为非负数,求a的取值范围.急用,
急急急····························
答
两式相加,3x+3y=1-3a,(1/3)×(1 - 3a)=(x+y)≥0,(1/3-a)≥0 ,a≤(1/3)