Question

(1)已知方程组4x-5y+2z=0和x+4y=3z,则x:y:z=____________________?

Answer 1

1

4x-5y+2z=0(1)

x+4y=3z(2)

(1)-(2)*4:

-21y+2z=-12z

y=2z/3

代入(1):

4x-10z/3+2z=0

x=z/3

x:y:z=z/3:2z/3:z=1:2:3

2.

解对4个方程式都适用

2x-3y=3(1)

3x+2y=11(2)

(1)*2+(2)*3:

13x=39

x=3

代入(1):

2*3-3y=3

y=1

把x=3,y=1代入含ab的方程：

3a+b=-1(3)

6a+3b=3(4)

(4)-(3)*2:

b=5

a=(-1-b)/3=-2