D=

1 1 1 1

1 2 - 1 4

2 -3 - 1 -5

3 1 2 1 1

=- 142

D 1=

5 1 1 1

-2 2 - 1 4

-2 -3 - 1 -5

0 1 2 1 1

=- 142

D2=

1 5 1 1

1 -2 - 1 4

2 -2 - 1 -5

3 0 2 1 1

=-284

D3=

1 1 5 1

1 2 -2 4

2 -3 -2 -5

3 1 0 1 1

=-426

D4=

1 1 1 5

1 2 - 1 -2

2 -3 - 1 -2

3 1 2 0

= 142

So x 1=D 1/D= 1.

x2=D2/D=2

x3=D3/D=3

x4=D4/D=- 1