求limn→∞[√(n4+n+1)-n2](n+3)．
1/2 limn→∞[√(n4+n+1)-n2](n+3) =limn→∞(n4+n+1-n4)(n+3)/[√(n4+n+1)-n2] =limn→∞(1+1/n)(1+3/n)/[√(1+1/n3+1/n4)+1]=1/2
求limn→∞[√(n4+n+1)-n2](n+3)．
1/2 limn→∞[√(n4+n+1)-n2](n+3) =limn→∞(n4+n+1-n4)(n+3)/[√(n4+n+1)-n2] =limn→∞(1+1/n)(1+3/n)/[√(1+1/n3+1/n4)+1]=1/2
