解方程组：3x+2y+2z=5 2x+3y+2z=7 2x+2y+3z=9

题目

解方程组：3x+2y+2z=5 2x+3y+2z=7 2x+2y+3z=9

答案

3x+2y+2z=5 (1)
2x+3y+2z=7 (2)
2x+2y+3z=9 (3)
(1)+(2)+(3)
7x+7y+7z=21
所以x+y+z=3
所以2x+2y+2z=6 (4)
(1)-(4),x=-1
(2)-(4),y=1
(3)-(4),z=3