A=(17^18+1)/(17^19+1)
17A=17(17^18+1)/17^19+1=17^19+17/17^19+1
17A=(17^19+1)+16/(17^19+1)=1+16/17^19+1
B=(17^17+1)/(17^18+1)
17B=17(17^17+1)/17^18+1=17^18+17/17^18+1
17B=(17^18+1)+16/(17^18+1)=1+16/17^18+1
Từ (1) và (2)⇒1+16/17^19+1<1+16/17^18+1
=> 17A<17B
Hay A<B
Vậy A<B