已知：3/X=4/Y=5/Z,求（X-2Y+4Z)/(4X+5Y)的值
人气：102 ℃ 时间：2020-02-20 15:04:25
解答
设3/X=4/Y=5/Z=1/K
x=3k
y=4k
z=5k
X-2Y+4Z=(3-8+20)k=15k
4X+5Y=(12+20)k=32k
（X-2Y+4Z)/(4X+5Y)=15/32
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