# Math

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20
(Sigma Sign) 2n + 7
k= 1

• Math -

∑2n+7
=2∑n + ∑ 7
=2*(20+1)(20/2) + 20*7
=420+140
=560

• Math -

Thank you, MathMate.

• Math -

Wait, do you know how it could be plugged into the Sn= a1 (1 - r^n/ 1 - r) formula?

• Math -

Sn= a1 (1 - r^n/ 1 - r)
applies when the series is a geometric progression, such as

20
∑ a1*r^i
i=1

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