已知实数x,y满足|x|+x+y=10、x+|y|-y=12,则x+y的值?

若x≤0,|x| = - x
|x| +x +y = 10
y = 10
代入 x+|y|-y=12 得 x = 12 > 0
矛盾,∴ x > 0
2x + y = 10 ①
若y≥0,x + |y| - y = x = 12
y = 10 - 2x < 0 ,矛盾
∴ y < 0
x - 2y = 12 ②
联立①②解得 x = 32/5,y = - 14/5
x + y = 18/5