求极限limn→∞(1/n-2/n+3/n-4/n+…+(2n-1)/n-2n/n).
limn→∞(1/n-2/n+…+(2n-1)/n-2n/n) =limn→∞(1+3+5+…+2n-1)-(2+4+6+…+2n) =limn→∞[n2-n(n+1)]/n =limn→∞(-n/n)=-1
求极限limn→∞(1/n-2/n+3/n-4/n+…+(2n-1)/n-2n/n).
limn→∞(1/n-2/n+…+(2n-1)/n-2n/n) =limn→∞(1+3+5+…+2n-1)-(2+4+6+…+2n) =limn→∞[n2-n(n+1)]/n =limn→∞(-n/n)=-1