Question

☆ONLY FOR MODERATORS OR MATHS GENIUS☆

$find \: the \: sum \: of \: first \: 20 \: terms \: of \: \\ the \: series \\ 2 + 13 + 28 + 47 + 70.......$
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♡SOLUTION MUST
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Answer 1

$\bold{ \huge{ \color{red}{ \fbox{ \ulcorner{ \: \star \: answer\star\: \urcorner}}}}}$

Here,

$\bold{ \large{ \color{blue}{ \fbox{ \ulcorner{ \: \star \:topic - ap \star\: \urcorner}}}}}$

Here,

a=2

D=13-2=11

So,

D=11

Also:-

n=20

Using the formula:-

S20=20/2.[2×2+{20-1}×11]

S20=10×(4+209)

S20=10×213

S20=2130

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