x^2-2xy+x-y=27 3x^2-6xy+2y=42方程组

x^2-2xy+x-y=27 (1)
3x^2-6xy+2y=42 (2)
(1)*3-(2)
3x-5y=39
y=3x/5-39/5
代入(1)
求出x
在代入y=3x/5-39/5求出y即可

x^2-2xy+x-y=27..........1
3x^2-6xy+2y=42...........2

1式*3-2式得
3x-5y=27
3x=27+5y
9x^2=25y^2+270y+729

1式*9得
9x^2-18xy+9x-9y=243
25y^2+270y+729-6*(27+5y)y+3*(27+5y)-9y=243
5y^2-114y-567=0
(y-27)(5y+21)=0
y=27或y=-21/5

x=54或x=2