SOLUTION: Find the number of terms of the sequence 1,4,7,10... Must be taken if the sum is to exceed 100.

Question 389888: Find the number of terms of the sequence 1,4,7,10... Must be taken if the sum is to exceed 100.
Answer by ewatrrr(24785) (Show Source): You can put this solution on YOUR website!



Hi,        

Find the number of terms of the sequence 1,4,7,10... for 

 In this example d = 3 and first term is = 1

    n/2 [2 + 3(n-1)] > 100

     n[2 + 3n-3)] > 200

     2n + 3n^2-3n > 200

    3n^2 - n - 200 = 0  n=-8 or n= 8  1/3



  Nine terms must be taken for sum to be > 100