> restart; with(plots):
  interface(displayprecision = 4):
  fnt:= 'style = point,
         symbol = cross,
         symbolsize = 15,
         size = [400,350],
         axes = normal,
         axesfont = [Courier, normal, 10],
         labelfont = [Courier, normal, 12],
         labels = [x, y]':

> M:= [[2.1,  .425],

     [2.2,  .351],
     [2.4,  .281],
     [2.6,  .228],
     [2.7,  .137],
     [2.8,  .163],
     [2.9,  .084],
     [3.0,  .047],
     [3.1,  .013],
     [3.3, -.048],
     [3.5, -.099],
     [3.7, -.142]]:

> plot({seq(M[i], i = 1..nops(M))},
    x = 2..4,
    fnt);

> S:= (m, b) -> sum((y[i] - f(x[i]))^2, i = 1..n);

S(m, b);

> gln:= {diff(S(m,b), m) = 0, diff(S(m,b), b) = 0}:

gln[1];
gln[2];

> lgn:= solve(gln, {m, b}):
  lgn[1];

lgn[2];

> n:= nops(M);

for j to n do
  x[j]:= M[j,1]:
  y[j]:= M[j,2]:
od:

> lgn: assign(lgn):

m:= evalf(m, 4);
b:= evalf(b, 4);

> Punkte:= plot({seq(M[i], i = 1..n)},
    x = 2..4,

  fnt):
Gerade:= plot ([f(x)], x = 2..4,
  style = line,
  color = blue):
display ([Punkte, Gerade]);