Question

Which expression is equivalent to *picture attached*

Answer 1

Answer:

$\sum_{n=3}^{20}(n(n+1))=\sum _{n=3}^{20} n^2+ \sum _{n=3}^{20} n$

Step-by-step explanation:

Given expression : $\sum_{n=3}^{20}(n(n+1))$

Solving further :

$\Rightarrow \sum_{n=3}^{20}(n^2+n)$

$\Rightarrow \sum _{n=3}^{20} n^2+ \sum _{n=3}^{20} n$

So, $\sum_{n=3}^{20}(n(n+1))=\sum _{n=3}^{20} n^2+ \sum _{n=3}^{20} n$

So, The given expression is equivalent to Option A

So, Option A is the answer