Đáp án:
`a)Q=((sqrtx-2)/(x-1)-(sqrtx+2)/(x+2sqrtx+1))*(1-x)^2/2`
`Q=((sqrtx-2)/((sqrtx-1)(sqrtx+1))-(sqrtx+2)/(sqrtx+1)^2)*(x-1)^2/2`
`Q=(((sqrtx-2)(sqrtx+1)-(sqrtx+2)(sqrtx-1))/((sqrtx+1)^2(sqrtx-1)))*(x-1)^2/2`
`Q=((x-sqrtx-2-x-sqrtx+2)/((sqrtx+1)^2(sqrtx-1)))*(x-1)^2/2`
`Q=(-2sqrtx)/((x-1)(sqrtx+1))*(x-1)^2/2`
`Q=-sqrtx(sqrtx-1)`
`b)Q>0`
`<=>-sqrtx(sqrtx-1)>0`
`<=>sqrtx(sqrtx-1)<0`
Vì `sqrtx>sqrtx-1`
`=>sqrtx>0,sqrtx-1<0`
`<=>0<x<1`
`c)Q=-sqrtx(sqrtx-1)`
`=-x+sqrtx`
`=-(x-sqrtx)`
`=-(x-sqrtx+1/4)+1/4`
`=-(sqrtx-1/2)^2+1/4<=1/4`
Dấu "=" xảy ra khi `sqrtx=1/2<=>x=1/4.`
