3a-2b=11---- (1)3(x+y)-2(x-y)=11------(2)comparea=(x+y)b=(x-y)a=3 所以 x+y=3
x+y=a=3
3a-2b=3（x+y)-2（x-y) 4a+3b=4（x+y)+3（x-y) x+y=a =3
x+y=3 x-y=-1 x=1 y=2
x+y=a=3X-y=b=-1x=1 y=2
