function [w, yA, MutlakHata, K, F, A, B, X, Y] = eliptiksonlufark(a,b,c,d,N,M)

% U_xx + U_yy = f , U(a,y)=fxa, U(b,y)=fxb, U(x,c)=fyc, U(x,d)=fyd

f = @(x,y) ...;
fxa = @(x,y) ...;
fxb = @(x,y) ...;
fyc = @(x,y) ...;
fyd = @(x,y) ...;

h = (b-a)/N;
k = (d-c)/M;

x = a:h:b;
y = c:k:d;

lambda = (h^2)/(k^2);
mu = 2*(1+lambda);


% A ve B matrisleri

for i = 1:M-1
    A(i,i) = mu;
    B(i,i) = -1;
end

for i = 1:M-2
    A(i,i+1)=-lambda;
    A(i+1,i)=-lambda;
end

% Katsayılar Matrisi

K = zeros((N-1)*(M-1));

for i = 1:N-1
    K(1+(i-1)*(M-1):i*(M-1), 1+(i-1)*(M-1):i*(M-1)) = A;
end

for i = 1:N-2
    K(1+(i-1)*(M-1):i*(M-1), 1+i*(M-1):(i+1)*(M-1)) = B;
    K(1+i*(M-1):(i+1)*(M-1), 1+(i-1)*(M-1):i*(M-1)) = B;
end

% Sağtaraf F Vektörü

F(1,1) = -(h^2)*f(x(2),y(2)) + fxa(a,y(2)) + lambda*fyc(x(2),c);
for i = 2:M-2
    F(i,1) = -(h^2)*f(x(2),y(i+1)) + fxa(a,y(i+1));
end
F(M-1,1) = -(h^2)*f(x(2),y(M)) + fxa(a,y(M)) + lambda*fyd(x(2),d);

for i=3:N-1
    F(1+(i-2)*(M-1),1) = -(h^2)*f(x(i),y(2)) + lambda*fyc(x(i),c);
    for j = 2:M-2
        F(j+(i-2)*(M-1),1) = -(h^2)*f(x(i),y(j+1));
    end
    F((i-1)*(M-1),1) = -(h^2)*f(x(i),y(M)) + lambda*fyd(x(i),d);
end

F(1+(N-2)*(M-1),1) = -(h^2)*f(x(N),y(2)) + fxb(b,y(2)) + lambda*fyc(x(N),c);
for i = 2:M-2
    F(i+(N-2)*(M-1),1) = -(h^2)*f(x(N),y(i+1)) + fxb(b,y(i+1));
end
F((N-1)*(M-1),1) = -(h^2)*f(x(N),y(M)) + fxb(b,y(M)) + lambda*fyd(x(N),d);

% Sayısal Sonuçlar

ww = K\F;

for i = 1:N+1
    w(1,i) = fyc(x(i),c);
    w(M+1,i) = fyd(x(i),d);
end

for j = 1:M+1
    w(j,1) = fxa(a,y(j));
    w(j,N+1) = fxb(b,y(j));
end

for j = 2:N
    for i = 2:M
        w(i,j) = ww((i-1) + (M-1)*(j-2));
    end
end

[X,Y] = meshgrid(x,y);

yA = ...; 
    
MutlakHata=abs(yA - w);