Hello,Originally Posted byNimmy

to 2.) I hope you meant . Then you can transform this term to:

and thats (n-1)*n which doesn't converge for n to infinity.

to 3. Split the summation into two sums: In 1st sum n is even and the numbers are positive, in the 2nd sum n is odd and all numbers are negative. Calculate both sums separately.

This sum must converge according to the convergence criterium of Leibniz.

Greetings

EB