Which expression is equivalent to picture attached

Question

asked Jan 12, 2021 151k views

1 Answer

Lurifaxel · Answer 1 · 2021-01-15T22:54:49+0000

Answer:

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

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