dont we have some ready-made formula for the questions which ask to find sum of a given series and the common difference between the terms is in. AP Normal summation method takes a lot of time

Hi If the differences are in A.P then general term is of the form an^2+bn+c You have to substitute the first three terms and solve simultaneous equations and obtain the values of a,b and c and then apply summation for each . This is the only approach for such questions .