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What is ∑n=16[4(−5)n−1]∑n=16[4(−5)n−1] equal to?

 

 May 16, 2018

Best Answer 

 #1
avatar+972 
+2

Hey Hev!

 

When n = 1,

 

\(4(-5)^{1-1}=4(-5)^0=4\cdot1=4\)

 

When n = 2, 

 

\(4(-5)^{2-1}=4(-5)^1=4\cdot-5=-20\)

 

When n = 3,

 

\(4(-5)^{3-1}=4(-5)^2=4\cdot25=100\)

 

We can tell there is a pattern with multiplying by -5. 

 

The next three terms in order are -500, 2500, and -12500

 

You add them to find the solution,

 

I hope this helped,

 

Gavin

 May 16, 2018
 #1
avatar+972 
+2
Best Answer

Hey Hev!

 

When n = 1,

 

\(4(-5)^{1-1}=4(-5)^0=4\cdot1=4\)

 

When n = 2, 

 

\(4(-5)^{2-1}=4(-5)^1=4\cdot-5=-20\)

 

When n = 3,

 

\(4(-5)^{3-1}=4(-5)^2=4\cdot25=100\)

 

We can tell there is a pattern with multiplying by -5. 

 

The next three terms in order are -500, 2500, and -12500

 

You add them to find the solution,

 

I hope this helped,

 

Gavin

GYanggg May 16, 2018

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