已知a/3=b/4=c/5,且a-2b+3c=5,则2a+b-4c=
问题描述：
已知a/3=b/4=c/5,且a-2b+3c=5,则2a+b-4c=
答
a:b:c=3:4:5,b=2,a=1.5,c=2.5,原式=-5
答
∵ a/3 = b/4 = c/5
∴设 a=3x,b=4x,c=5x
a-2b+3c = 5
3x - 8x+15x = 5
10x = 5
x = 1/2
2a+b - 4c
= 6x + 4x - 20x
= - 10x
= - 5