已知m,n是有理数,不等式3m-4n+(2m-n)x<0和-9x+4<0的解集相同,求不等式2m-3n+(m-4n

显示全部楼层 · 2011-12-22 18:54:04

-9x+44x>4/93m-4n+(2m-n)x0>x>(3m-4n)/(n-2m)则（3m-4n)/(n-2m)=4/94(n-2m)=9(3m-4n)4n-8m=27m-36n40n=35m8n=7mn>2m 则m02m-21/8m+(m-7/2m)x>0-5/8-5/2x-16/25...

千问 · 2011-12-22 18:54:04

解：依题意得-9x+44
x>4/93m-4n+(2m-n)x0>x>(3m-4n)/(n-2m)
则（3m-4n)/(n-2m)=4/94(n-2m)=9(3m-4n) 4n-8m=27m-36n
40n=35m8n=7m...

千问 · 2011-12-22 18:54:04

-9x+44
x>4/93m-4n+(2m-n)x0>x>(3m-4n)/(n-2m)
则（3m-4n)/(n-2m)=4/94(n-2m)=9(3m-4n) 4n-8m=27m-36n
40n=35m8n=7mn>2m 则...

千问 · 2011-12-22 18:54:04

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千问 · 2011-12-22 18:54:04

-9x+44/9所以，2m-n必小于0，x>(4n-3m)/(2m-n)2m-n=9,4n-3m=4,则m=8,n=7,若是4/9的倍数，不满足有理数。式子化为2*8-3*7+(8-4*7)x>0，20x<-5,x<-1/4...