Could you please tell me how to find the summation of a series whose difference of difference (2nd order difference) of successive terms is a constant.
Ex- 3+4+9+18+31+...... 1st order difference is 4-3=1
18-9=9. 31-18=13 Second order difference is 5-1=4, 9-5=4, 13-9=4
Hence second order difference is a constant.so how do you find the summation of such a series upto n terms.
Also it would be helpful if you could explain a general procedure if the nth order difference was a constant.
Thanks in advance.
P.s would be grateful to anyone who would reply at the earliest as I need it for an exam the day after tomorrow