... c´o 2 x− x 2 x − 2 = 2 x− 2 2− (x 2 − 2 2)x − 2 =4· 2 x 2 − 1x− 2 −x 2 − 4x − 2 ·T`u.d´o suy r˘a`nglimx 2 2x− x 2 x − 2 = 4 limx 2 2x 2 − 1x − 2 − limx 2 x 2 − 4x − 2 = ... 22 ; 0, 22 2; ,0, 22 2 n, Chı’dˆa˜n. Biˆe’udiˆe˜n andu.´o.ida.ngan=0, 22 2= 2 10 + 2 10 2 + ···+ 2 10 n(DS. lim an =2/ 9)7 .2. Gi´o.iha.n h`am mˆo.tbiˆe´n 29 Tru.`o.ng ... hˆo.itu.1) an=n 2 − 1n 2 2) an =2+ 1 2! +13!+ ···+1n!Chı’dˆa˜n. T´ınh bi.ch˘a.ndu.o..csuyt`u.n! 2 n−1v`a do d´oan 2+ 1 2 +1 2 2+ ···+1 2 n−1=3−1 2 n−1< 3.4....