Question

3 with the check mark symbol that goes over 375 divided by 3 that goes over the check mark symbol that goes over 3. Sorry can't remember what that sign is

Answer 1

evaluate the sum of the first n terms of the sefies 1,2,3,+2,3,4,+3,4,5,+...+n(n+1)(n+2),what the sum for n=10,20,25.