诛仙3 草庙村要求:满脑子都是x,y! help me!!!

来源：百度文库 编辑：高考问答 时间：2024/05/10 09:07:31
已知方程组2x+y=2k,2y-x=3的解x<1,y>1,求整数k.

x=2y-3
∵x<1，∴y<2，又∵y>1，∴1<y<2
2k=2x+y=4y-6+y=5y-6，∴k=2.5y-6
∵1<y<2，∴-3.5<k<-1，∴整数k为-3或-2

原方程组相当于2x+y=2k
4y-2y=6
解得 y=2k+6/5 x=4k-3/5
根据已知条件x<1 y>1得 2k+6/5>1
4k-3/5<1
-1/2 <k<2

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