例1:求下列极限 im n→0 n→00 2n2+n 3n3+n n→>3n2+2 n→>00 2n+-n 3n3+ lim(+-3) 解:(4)lim n→ =im n→>2n4-n2n→ m lim =+lim n→)0 n→ 0+0 0 lim 2-lim 2-0例1：求下列极限 ) 1 2 (1) lim ( 2 n n n + → 3 2 2 (3) lim 2 2 n + + → n n n n 3n 2 (2) lim n − → 4 2 3 n 2 3 (4) lim n n n n − + → 3 3 3 4 2 2 2 3 2 3 1 3 1 lim( ) 3 : (4) lim lim 2 1 1 2 lim(2 ) 3 1 lim lim 0 0 0. 1 2 0 lim 2 - lim n n n n n n n n n n n n n n n n n n n n n →  → → →  → → → → + + + = = − − − + + = = = − 解 11