destinyw9619 destinyw9619

21-01-2018
Mathematics

contestada

Write a formula for the sum of the first n integers that are divisible by 3

Respuesta :

dannielle dannielle

21-01-2018

3*1+3*2+3*3+,,,+3n= 3*(1+2+...+n)
=3*n(n+1)/2

cause 1+2+...+n=n(n+1)/2

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