diff --git a/t4.m b/t4.m
new file mode 100644
index 0000000..5e51437
--- /dev/null
+++ b/t4.m
@@ -0,0 +1,13 @@
+clear,clc
+A=[1 1 0 3;
+   2 1 -1 1;
+   3 -1 -1 2;
+  -1 2 3 -1]
+
+[L1,U1]=lu_decompose(A)
+
+B=[8;7;14;-7]
+    
+V=inv(L1)*B
+
+X=inv(U1)*V