`a)A=[2/(x+1)^3 (1/x+1)+1/(x^2 +2x+1)(1/x^2+1)]:(x-1)/x^4`

`=[2/(x+1)^3 .(x+1)/x +1/(x+1)^2 . (1+x^2)/x^2 ]:(x-1)/x^4`

`=[2/(x(x+1)^2)+(1+x^2)/(x^2 (x+1)^2)]:(x-1)/x^4`

`=(2x+1+x^2)/(x(x+1)^2) . x^4/(x-1)`

`=(x+1)^2/(x+1)^2 . x^3/(x-1)`

`=x^3/(x-1)`

`b)A<0`

`<=>x^3/(x-1)<0`

`<=>[({(x^3 >0),(x-1<0):}),({(x^3 <0),(x-1>0):}):}`

`<=>[({(x>0),(x<1):}(n)),({(x<0),(x>1):}(l)):}`

`<=>0<x<1`

Vậy `A<0<=>0<x<1`

`\sqrt{\sqrt{5}-\sqrt{3-\sqrt{20}+3}}`

`=\sqrt{\sqrt{5}-\sqrt{6-2\sqrt{5}}}`

`=\sqrt{\sqrt{5}-\sqrt{5-2\sqrt{5}+1}}`

`=\sqrt{\sqrt{5}-\sqrt{(\sqrt{5}-1)^2}}`

`=\sqrt{\sqrt{5}-|\sqrt{5}-1|}`

`=\sqrt{\sqrt{5}-\sqrt{5}+1}`

`=\sqrt{1}`

`=1`

xem lại pài

`MC=24`

Ta có:

`3/8=9/24`

`5/6=20/24`

`4/3=32/24`

`13/12=26/24`

`5/4=30/24`

`=>9/24<20/24<26/24<30/24<32/24`

`=>3/8<5/6<13/12<5/4<4/3`

`16xx48+16xx24+16xx28`

`=16xx(48+24+28)`

`=16xx100`

`=1600`

`325-317+426-418`

`=(325-317)+(426-418)`

`=8+8`

`=16`

`2%` của `2` tấn là:

`2%xx2=0,04 (tấn)=0,04 xx 1000 kg= 40(kg)`

`3 2/4+4 4/7`

`=3 1/2 +32/7`

`=7/2+32/7`

`=49/14+64/14`

`=113/14`