So sánh hai phân số sau : A= 7^99+2/7^100+2; B=7^98+2/7^99+2
Giải thích
Ta có:
+) A<1⇒799+27100+2<55⇒799+17100+1<799+2+57100+2+5=799+77100+7=798+1799+1
+) 798+1799+1<1⇒798+1799+1<11⇒798+1799+1<798+1+1799+1+1=798+2799+2
+ Vậy A<B.
Ta có:
+) A<1⇒799+27100+2<55⇒799+17100+1<799+2+57100+2+5=799+77100+7=798+1799+1
+) 798+1799+1<1⇒798+1799+1<11⇒798+1799+1<798+1+1799+1+1=798+2799+2
+ Vậy A<B.