若x/2=y/3=z/4,且3X-2y+5z=20,求X+3y-z
问题描述:
若x/2=y/3=z/4,且3X-2y+5z=20,求X+3y-z
答
设x/2=y/3=z/4=m
则x=2m,y=3m,z=4m
3x-2y+5z=20
6m-6m+20m=20
20m=20,m=1
x=2,y=3,z=4
x+3y-z=2+3×3-4=7