解不等式…

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2 | 2012-10-26 22:39:28 | 显示全部楼层 |阅读模式

-4x2+4x-1>0-(4x2-4x+1)=-(2x-1)2>0(2x-1)2≥0,所以无解 x+1+5x2/(x+2)>=1/(1-x)x+1+5x2/(x+2) - 1/(1-x)≥0通分得(x+1)(x-1)(x+2)/(x-1)(x+2)+5x2(x-1)/(x-1)(x+2)+(x+2)/(x-1)(x+2)≥0[(x+1)(x-1)(x+2)+5x2(x-1)+x+2]/(x-1)(x+2)≥0分子化简(6x3-3x2)/(x-1)(x+2)≥03x2(2x-1)/(x-1)(x+2)≥0到这里就可以用穿针引线法解题...

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