分母是c(x+d/c)原式=[a(x+d/c-d/c)+b]/c(x+d/c)=[a(x+d/c)-ad/c+b]/[c(x+d/c)]=a(x+d/c)/[c(x+d/c)]+(b-ad/c)/[c(x+d/c)]=a/c+(b-ad/c)/(cx+d)
