14+a=3
21-b=4
则a=-11,b=17
代入2(x+y)+a(x-y)=3,3(x+y)-b(x-y)=4
2(x+y)-11(x-y)=3①
3(x+y)-17(x-y)=4②
由①得2x+2y-11x+11y=3
13y-9x=3③
由②得3x+3y-17x+17y=4
20y-14x=4
10y-7x=2④
③*7-④*9得91y-90y=21-18
y=3
把y=3代入④中得x=4
∴x=4 y=3
14+a=3
21-b=4
则a=-11,b=17
代入2(x+y)+a(x-y)=3,3(x+y)-b(x-y)=4
2(x+y)-11(x-y)=3①
3(x+y)-17(x-y)=4②
由①得2x+2y-11x+11y=3
13y-9x=3③
由②得3x+3y-17x+17y=4
20y-14x=4
10y-7x=2④
③*7-④*9得91y-90y=21-18
y=3
把y=3代入④中得x=4
∴x=4 y=3