|X+Y-2| ≥0 ；(X-3Y+5)^2 ≥ 0 |X+Y-2|与(X-3Y+5)^2互为相反数 X+Y-2 =0 ；X-3Y+5 = 0 x=1/4,y=7/4,1,因为 | X+Y-2| ≥0 (X-3Y+5)^2 ≥ 0 互为相反数 ， 所以X+Y-2 X-3Y+5 只能等于0 X+Y-2 =0 X-3Y+5 = 0 2元一次方程 解得x=1/4，y=7/4,1,
