... gi´o.iha.ncu’a d˜ay: 0, 2; 0, 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 10n(DS. lim an =2/ 9)10 Chu.o.ng 7. ... b)(a 2 − ab + b 2 )suy raan=3√n 2 − n3+ n3√n 2 − n3 2 − n3√n 2 − n3+ n 2 3√n 2 − n3 2 − n3√n 2 − n3+ n 2 =n 2 3√n 2 − n3 2 − n3√n 2 − n3+ n 2 =1[1/n ... nˆen1+1 2 + ···+1 2 n= 2( 2n− 1) 2 n,1+13+ ···+13n=3(3n− 1) 2 · 3nv`a do d´o:lim an= lim 2( 2n− 1) 2 n· 2 · 3n3(3n− 1)= 2 lim 2 n− 1 2 n· 2 3lim3n3n− 1= 2 lim[1...