Question

解线性方程组{x1+2x2+x3=10,2x1+5x2+3x3=20,x1+x2+3x3=13}

Answer 1

1 2 1 10 (1)

2 5 3 20 (2)

1 1 3 13 (3)

(2)+(3)=[3 6 6 33]

(1)=[3 6 3 30]

所以x3=1,继而解出X1= 11,X2= -1