find the sum of s100 for An= 5n + 3

Question

find the sum of s100 for An= 5n+3

Answer 1

The sequence is 8, 13, 18, 23, ...

 

The sequence is arithmetic with common difference d = 5.  

 

S_n = sum of first n terms = (n/2)[a₁ + a_n]

 

S₁₀₀ = (100/2)[a₁ + a₁₀₀] = 50[8 + 503] = 50(511) = 25,550