Following series is given upto n terms:
It's sum up to n terms is defined by the formula:
( a,b,c,d are integer constants . )
What is a+b+2c+d?
Try splitting each term into a series. \((12-1)=?\) And \((1234-123)=?\).
Try finding formula upto n terms by summation (then deduce to the above equation) and then compare coefficients to the above equation and just sum to give the answer.