express the sum using summation notation
3+12+27+...+75

Question

express the sum using summation notation 
3+12+27+...+75

sdfgsdfgs · Answer

is there any missing number there? the prob seems incomplete....

anonymous · Answer

no thats all it says!:(

sdfgsdfgs · Answer

it didnt say how many terms there are in the "..." part?

anonymous · Answer

no thats it thats the question....

geerky42 · Answer

Terrific teacher you have right there...

sdfgsdfgs · Answer

thanx @geerky42 but im out of idea w/ whats given. how about u? :)

geerky42 · Answer

I am talking about nanacuba's teacher lol was being sarcastic.

No idea either. Impossible to determine pattern just by what we are given so far.

anonymous · Answer

I have the answer but its a hw so im supposed to show work
its 
$$\sum_{k=1}^{2} 3k^2$$

anonymous · Answer

i just don't know how to get there

geerky42 · Answer

Just from k=1 to 2?

But on question, you have at least 4 terms...?

anonymous · Answer

sorry my bad its $$\sum_{k=1}^{5}3k^2$$

geerky42 · Answer

Hmm. Now I see it.

You can start by factor 3 out from all terms, so you have $3(1+4+9+\cdots+25)$

From here, we can see pattern and it's square number from 1 to 5.

geerky42 · Answer

should have looked at GCF along these terms lol...

anonymous · Answer

lol thanks now I see it too!!!

sdfgsdfgs · Answer

Good one but its not that obvious