Question

解方程组{x+2y+z=4 2x+y+2z=5 x+y+3z=5

Answer 1

x+2y+z=4 ①

2x+y+2z=5 ②

x+y+3z=5 ③

2①-③＝3y＝3

y＝1 ④

②-③＝x-z＝0

x＝z ⑤

将④,⑤代入①

x+2+x=4

x=1=z

所以x=1,y=1,z=1