dx=2;
dt=1;
x=[2:dx:10];
n=length(x)-1;
lambda=0.020875;

T0=100;
T5=50;

A=zeros(n,n);
B=zeros(n,1);

for k=1:n
A(k,k)=(1+2*lambda);

if k==1
%don't do left of diagonal
B(k,1)=lambda*T0;
else
A(k,k-1)=-lambda;
end

if k==n
%don't do right of diagonal
B(k,1)=lambda*T5;
else
A(k,k+1)=-lambda;
end

end