[i]Program Task47;
[i]Var
x1,y1,x2,y2,x3,y3,x4,y4,xk,yk,dx,dy,a1,b1,c1,a2,b2,c2 : Real;
Begin
write('x1=');
readln(x1);
write('y1=');
readln(y1);
write('x2=');
readln(x2);
write('y2=');
readln(y2);
write('x3=');
readln(x3);
write('y3=');
readln(y3);
a1:=y2-y3;
b1:=x3-x2;
c1:=x2*y3-x3*y2;
a2:=b1;
b2:=-a1;
c2:=-b1*x1+a1*y1;
xk:=(b1*c2-b2*c1)/(a1*b2-a2*b1);
yk:=(c1*a2-c2*a1)/(a1*b2-a2*b1);
dx:=(xk-x1)*2;
dy:=(yk-y1)*2;
x4:=x1+dx;
y4:=y1+dy;
writeln ('x4=',x4:0:3);
writeln ('y4=',y4:0:3);
Readln;
End.