简单计算一下即可，答案如图所示
f(cx-az,cy-bz)=0 设u=cx-az, v=cy-bzZ=Z(u,v)方程两边对x求偏导cfu-aZx'fu-bZ'xfv=0Zx'=cfu/(afu+bfv)方程两边对y求偏导-aZy'fu+cfv-bZy'fv=0Zy'=cfv/((afu+bfv)aZx'+bZy'=(acfu+bcfv)/(afu+bfv)=c
