Plotting the graph of an exact solution against a discrete solution

So the problem is asking to write a routine for the finite discrete solution with

-u''(x)=12x^2 ; domain x=[0,1] ; u'(0)=u(1)=0 ; deltax=1/(n+1)

I have a code but when I run it the plot for the exact solution is right but the discrete solution plot(marked by 'o') is way below it. I cannot figure out why it isn't closer (because I know it should be). Any help is appreciated. The first row of the matrix should be 1 -1 0 0 0..... because of the boundary conditions. Here is my code

function [delta_x] = Difference_Plot(n)
%Step size
delta_x = 1/(n+1);
%Discretized Domain
x_disc = (0:1/(n+1):1)';
%Toeplitz Matrix
T=zeros(n-1);
T(1,1)=1;
T(1,2)=-1;
for i=2:n-2
  T(i,i-1)=-1;
  T(i,i)=2;
  T(i,i+1)=-1;
end
for i=n-1
  T(i,i-1)=-1;
  T(i,i)=2;
end
disp(T)
%The function
f = 12*(x_disc(2:n)).^2;
%Discrete Solution
u_disc = T\((delta_x)^2*f);
x_exact=x_disc;
%Exact solution
u_exact = -(x_exact(2:n)).^4+1;
x_exact = (0:1/500:1)';
u_exact = -(x_exact).^4+1;
%Plot of exact solution
plot(x_exact, u_exact, 'r')
hold on
%Discrete solution
plot(x_disc(2:n), u_disc, 'o')
hold off