Question

find the sum of the first n natural numbers that's divisible by 3​

Answer 1

infinity is your answer

Answer 2

Answer:

3n² + 3n / 2

Step-by-step explanation:

This question can be solved by using the concept of ARITHMETIC PROGRESSION.

a = 3 ;

d = 3 ;

Sum : n/2 [ 2a + (n - 1)d ]

Put values.....

=> n/2 [ 2 × 3 + ( n - 1) × 3 ]

=> n/2 [ 3 + n ]

=> 3n² + 3n /2