r=(x,y,z)与rr=(xx,yy,zz)关于平面Ax+By+Cz+D=0对称,有
r=rr+2d n=(xx,yy,zz)+2 (A*xx+B*yy+C*zz+D)/sqrt(A^2+B^2+C^2) (A,B,C)/sqrt(A^2+B^2+C^2)
=(xx+2 (A*xx+B*yy+C*zz+D)*A/(A^2+B^2+C^2),yy+2 (A*xx+B*yy+C*zz+D)*B/(A^2+B^2+C^2),zz+2 (A*xx+B*yy+C*zz+D)*C/(A^2+B^2+C^2))
r满足f（x,y,z）＝0
rr满足 f（ xx+2 (A*xx+B*yy+C*zz+D)*A/(A^2+B^2+C^2),
yy+2 (A*xx+B*yy+C*zz+D)*B/(A^2+B^2+C^2),
zz+2 (A*xx+B*yy+C*zz+D)*C/(A^2+B^2+C^2) )＝0
这就是索求的方程