已知方程组ax+by=2;cx-dy=5的解是x=2;y=-1,所以2a-b=2,2c+d=5a(x-1)+b(y+2)=ax+by-a+2b得ax+by=3(a-b)c(x-1)-d(y+2)=cx-dy-c-2d得cx-dy=3(c+d)则方程组a(x-1)+b(y+2)=2;c(x-1)-d(y+2)=5的解是x=3,y=-3....