>>442
y2-y1=-2(x2-x1)
(y1+y2)/2=(1/2)(x1+x2)/2
をといて
{x2,y2}={{3,4},{4,-3}}/5 {x1,y1} から
A={{3,4},{4,-3}}/5
B={{cos(Pi/4),-sin(Pi/4)},{sin(pi/4),cos(pi/4)}}={{1,-1},{1,1}}/Sqrt[2]

f(g(X))<=> Ag == B
so
g=A^(-1)B
={{-1,7},{7,1}}Sqrt[2]/10