Giúp mik câu 1 a,b với

`a)`

`A=(92 - 1/9 - 2/10 - 3/11 - ... - 90/98 - 91/99 - 92/100)/(1/45 + 1/50 + 1/55 + ... + 1/495 + 1/500`

Tử số:

`92 - 1/9 - 2/10 - 3/11 - ... - 90/98 - 91/99 - 92/100`

`=1 - 1/9 + 1 - 2/10 + 1 -3/11 + ... + 1-92/100`

`=8/9 + 8/10 + 8/11 + ... + 8/100`

`=8.(1/9 + 1/10 + 1/11 + ... + 1/100)`

Mẫu số:

`1/45 + 1/50 + 1/55 + ... + 1/495 + 1/500`

`=1/5 . (1/9 + 1/10 + 1/11 + ... + 1/99 + 1/100)`

`=>A=(8.(1/9 + 1/10 + 1/11 + ... + 1/100))/(1/5 . (1/9 + 1/10 + 1/11 + ... + 1/99 + 1/100)) =(8)/(1/5)=40`

`b)`

`152=2.2.2.19=2^3 .19`

`112=2.2.2.2.7=2^4 .7`

`3^152 = (3^19)^8`

`4^112 = (4^14)^8`

Mà `3^19 > 4^14`

`=> (3^19)^8 > (4^14)^8` hay `3^152 > 4^112`.