Problem with finite difference

Hello !

In order to solve the following ODE : $U_{xx} + U_x - 2U + 2 = 0$ with boundary condition $U(-1) = 0 = U(1)$, I use centered differences of order 2 :

$U_{xx} = \frac{U_{i+1} - 2 U_i + U_{i-1}}{h^2} + O(h^2)$

$U_x = \frac{U_{i+1} - U_{i-1}}{2h} + O(h^2)$

Putting this altogether gives me the following code :

Mxx = gallery('tridiag',n+1,1,-2,1)*1/h^2;
Mx = gallery('tridiag',n+1,1,0,-1)*1/(2*h);
M0 = speye(n+1);
M = Mxx + Mx - 2*M0;
M(1,1) = 1; M(1,2) = 0;
M(end,end) = 1; M(end,end-1) = 0;
M = sparse(M);
B = [0;-2*ones(n-1,1);0];
U = M\B;

But the solution doesn't fit the analytical one at all... $u(x) = 1 - \frac{\sinh(2)e^x + \sinh(1)e^{-2x}}{\sinh(3)}$

Where is the mistake ?