因为两个是同类项,所以y + 4 = 2x - 2
3x - 1 = 1 - 2y
上式乘以2得,2y + 8 = 4x - 4
和2式相减得,3x - 9 = 5 - 4x
所以x = 2
解得y = -2
所以x² - y² = 0