Write the sum using summation notation, assuming the suggested pattern continues.

-9 - 3 + 3 + 9 + ... + 81

Question

Write the sum using summation notation, assuming the suggested pattern continues.

-9 - 3 + 3 + 9 + ... + 81

tkhunny · Answer

Unfortunately, with only a small number of values, the "suggested pattern" doesn't actually exist.

anonymous · Answer

I have these choices though @tkhunny

anonymous · Answer

oops, actually these are my choices

paxpolaris · Answer

lol better

anonymous · Answer

a=-9
d=-3-(-9)=-3+9=6
l=81
l=a+(n-1)d
81=-9+(n-1)6
n=?
then write as A.P. series

perl · Answer

thats a sum of a sequence that is linear

perl · Answer

plug in the top index, 15

-9 + 6*15 , that will give you the last value

tkhunny · Answer

Well, it's not $\infty$.
I wouldn't even look at "54", either.

anonymous · Answer

so a? @perl @surjithayer

anonymous · Answer

@tkhunny

anonymous · Answer

thank you so much! could you help me with a couple other different questions?

tkhunny · Answer

Why are you tagging anyone?  You have enough information to solve it.  Write down the correct answer and move onl

Post new question on new threads and ALWAYS show YOUR work.  Always!  No excuses.

anonymous · Answer

81+9=(n-1)6
n-1=81/6=15
n=15+1=16
n from 0 to 15 gives 16 terms
so first option matches this

anonymous · Answer

@surjithayer thank you(:

anonymous · Answer

yw