已知(a+b)/2=(b-2c)/3=(3c-a)/4,求(5a+6b-7c)/(8a+9b)的值.
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已知(a+b)/2=(b-2c)/3=(3c-a)/4,求(5a+6b-7c)/(8a+9b)的值.
已知(a+b)/2=(b-2c)/3=(3c-a)/4,求(5a+6b-7c)/(8a+9b)的值.
已知(a+b)/2=(b-2c)/3=(3c-a)/4,求(5a+6b-7c)/(8a+9b)的值.
因为a+b/2=b-2c/3=3c-a/4
设a+b/2=b-2c/3=3c-a/4=k
所以a+b=2k①,b-2c=3k②,3c-a=4k③
①-②:a+b-b+2c=2k-3k
a+2c=-k④
所以④+③:3c-a+a+2c=-k+4k
5c=3k
c=(3/5)k
同理可得:a= (-11/5)k b=(21/5)k
所以(5a+6b-7c)/(8a+9b)
=(-11k+126/5k-21/5k)/(-88/5k+189/5k)
=50/101
50/103我有答案
你看他们谁解的对?
8/27