What is the sum of the geometric sequence 8, -16, 32...where there are 15 terms. I got 87384 with formula.

Question

anonymous · Answer

I forgot to add...the sequence, so I know my answer is wrong. Please help!

zarkon · Answer

the sum is 87384

anonymous · Answer

OK, this is the same answer I came up with so I guess I'm right :) Did you use the geometrict Series Formula

zarkon · Answer

no...i used my calculator to find the sum (ti-nspire cas)

anonymous · Answer

Oh. I have a ti-84. How did you do this?

zarkon · Answer

i created a function for the sequence..called it $$f(n)$$

then I computed

$$\sum_{n=1}^{15}f(n)$$

;)

zarkon · Answer

you should be able to do it on the 84

I believe there is a sequence command

SEQ

anonymous · Answer

Wow..I'm not there yet in algebra so I guess I will keep working the old fashion way :)

anonymous · Answer

Thank you and bye...off to another problem!