x
+
3y
+
2z
=
13,
2x
+
y
+
z
=
7,
-x
+
2y
+
3z
=
12,
消元利用
-x
+
2y
+
3z
=
12,
-2x
+
4y
+
6z
=
24,
首先去掉
x,
5y
+
5z
=
25,
5y
+
7z
=
31,
2z
=
6,
z
=
3,
5y
+
5z
=
25,
y
+
z
=
5,
y
+
3
=
5,
y
=
2,
2x
+
y
+
z
=
7,
2x
+
5
=
7,
2x
=
2,
x
=
1,
解方程组,
x
=
1,
y
=
2,
z
=
3,