A $=$ diag $($ones $(1,4),1)+$ diag $($ones $(1,4),-1)-$

$2*$ eye $(5)$;

U $=$ A;

n $=$ length $($U$)$;

for j$=1$:n

if U$($j$,$ j$)==0$

error$(\text{'}$ System cannot be solved by regular Gaussian elimination.$\text{'})$;

end

U$$j$+1$:n$=$ Ulj$+1$:n$-$Ulj$+1$:n

$,$ j $/$ Ulj, j$)*$ U$($j$,$ :$)$;

end

L$=$ A $/$U;

disp $($U$)$;

disp $($L$)$;