> x1:=2;y1:=9;x2:=4;y2:=16;x3:=5;y3:=25;ep:=1/2;del:=1;
> S:=(y1-m*x1-b)^2+(y2-m*x2-b)^2+(y3-m*x3-b)^2;
> dSb:=diff(S, b);dSm:=diff(S,m);
> sols:=solve({dSm=0,dSb=0});
> slope:=evalf (subs(sols,m),4);intercept:=evalf (subs(sols,b),4);
> plot3d(S,m=slope-ep..slope+ep,b=intercept-del..intercept+del,axes=BOXED);
>