Đáp án+Giải thích các bước giải:
`a)Q=(xsqrtx-1)/(x-sqrtx)-(xsqrtx+1)/(x+sqrtx)+(x+1)/sqrtx(x>0,x ne 1)`
`Q=((sqrtx-1)(x+sqrtx+1))/(sqrtx(sqrtx-1))-((sqrtx+1)(x-sqrtx+1))/(sqrtx+1)+(x+1)/sqrtx`
`Q=(x+sqrtx+1)/sqrtx-(x-sqrtx+1)/sqrtx+(x+1)/sqrtx`
`Q=(x+sqrtx+1-x+sqrtx-1+x+1)/sqrtx`
`Q=(x+2sqrtx+1)/sqrtx`
`b)Q=sqrtx+2+1/sqrtx`
ÁP dụng bđt cosi cho 2 số dương ta có:
`sqrtx+1/sqrtx>=2`
`=>Q>=2+2=4`
Dấu "=" xảy ra khi `sqrtx=1/sqrtx<=>x=1(ktm)`
`=>Q>4`