Trial Q (1 Viewer)

[krypticlemonjuice]

In this question, how did they even get that highlighted identity??? Im so confused

 

[synthesisFR]

View attachment 39735

View attachment 39736

In this question, how did they even get that highlighted identity??? Im so confused

Geometric series?

 

[SadCeliac]

View attachment 39735

View attachment 39736

In this question, how did they even get that highlighted identity??? Im so confused

let me send a pic real quick

 

[SadCeliac]

View attachment 39735

View attachment 39736

In this question, how did they even get that highlighted identity??? Im so confused

 

[unofficiallyred12]

errrr since it's given that Sn = 0 if n is a multiple of 3, gp isn't needed. instead u can do w+w^2+...+w^3k + w^(3k+1) = 0 + w^(3k+1) = w and then do the same thing when sum is to 3k+2

 

[Luukas.2]

View attachment 39737

It would be quicker to do this as:

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[SadCeliac]

It would be quicker to do this as:

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cheers boss but I mean both work lol

 

[Luukas.2]

cheers boss but I mean both work lol

True, but it took me a while to figure out why your working was valid... it looks like you multiplied by but in fact you didn't... I thought others might have not been sure.