{2x+3y+2z=19{3x+2y+2z=17{2x+2y+3z=13

问题描述:

{2x+3y+2z=19
{3x+2y+2z=17
{2x+2y+3z=13

无解

{2x+3y+2z=19(1)
{3x+2y+2z=17(2)
{2x+2y+3z=13(3)
(1)-(2)得y-x=2即y=x+2(4)
(2)-(3)得x-z=4即z=x-4(5)
(4)(5)代入(1)得2x+3(x+2)+2(x-4)=19
得x=3
代入(4)得y=5
代入(5)得z=-1

三式相加得到:7(x+y+z) = 49,所以 x+y+z = 7,2x+2y+2z = 14 (1)
用三个式子分别减去 (1) 式即得:x = 3,y = 5,z = -1.

{2x+3y+2z=19--------1
{3x+2y+2z=17--------2
{2x+2y+3z=13--------3
2-1得x=
3-2得z=
y=