A.P Series with Sign change
  Enter the Number
  Enter common Difference
Enter no. of terms
Find Sum
 
Here the Series is of the type 1 - 3 + 5 - 7 + 9 -......
where the absolute value of numbers are in AP and the alternate terms change sign. They are of the type a + (a + r) + (a - r) + ( a + 2r ) + ( a - 2r )
Here first term is substracted from the second term to find common difference( c.d).
Test With--
1) 3 - 6 + 12 - 15 + 21 - 24 where 1st term is 3, c.d= - 9 ; no. of terms = 6
2) 3 - 6 + 12 - 15 + 21
U can construct the series by putting 1st term, c.d, and number of terms 1, 2, 3, 4 etc.