Math help

I’ve gone through this sheet of forty-two questions without a hitch except for four. Help plz! xD
(I also need to show full work for these things, just to make it worse) >.>

14. Solved by Daledude

20. Solved by Daledude

26. Evaluate: Sum up all the terms of 5(-2)^k-1 from, and including, K=3 to K=13
(This is in sigma notation, a 13 on the top and K=3 at the bottom)
(a) 13600
(b) 13655
(c) -13651.67
(d) -13646.67

(Note: I tried this question and got 13660)

27 is SOLVED, Thanks Daledude

(Note: I don’t believe our teacher has taught us this one yet as all the formulas in my notes do not correlate with this one)

33. Determine the value of K for the geometric sequence: 8, K, 20
(a) (10^1/2)/2
(b) 2(10^1/2)
(c) 4(5^1/2)
(d) 4(10^1/2)

I need the answers by tomorrow. (and this was also given just today) If you help, you get:
A cookie
A big-assed thanks from me
A rep (possibly x2)

what grade are you in?

12. >.> I know, I’m an idiot.

so am I.
I’ll give it a shot.

The sheet has answers, he wants us to show work, that’s the problem. >.> I can’t make sense of these things and I have a test for it tomorrow. (again, just given to us today)

*puts down calculator*

ok then, Im no help,lol

lol well, you know, thanks for trying anyway.

Just figure out which number plugs in where and then make it look like you did the work. Or you can look at the point in the chapter in the book where it explains it. Algebra II amirite?

Damn If only I were stereotypical chinese exchange student!

Indalecio wrote: Just figure out which number plugs in where and then make it look like you did the work. Or you can look at the point in the chapter in the book where it explains it. Algebra II amirite?

It’s geometric sequences, we don’t have Algebra II like you American guys do. (I’m Canadian don’t forget, our education system is fraked up)

Well the definition of a geometric sequence is that a(n+1)/a(n)=r (parentheses are subscript). I would try plugging in all the possible answers and see which ones give you a constant for r.

I’m determined to live forever, or die trying. - Yossarian

For 26 I’ll bet you just plugged it into the calculator wrong. It’s just adding numbers after all...

For 27 it’s just the formula A=P(1 r/n)^nt

P= starting cash
r= rate (7%=.07)
n= number of times compounded per unit of time (quarterly = 4 per year)
t= time

For 33 I think you could do 20/r^2=8. That would give you r. Then multiply 8 by r to get K. Just remember that because you took the root of a square that your answer can be positive or negative.

Although when I worked it out this way it didn’t correspond to any of the answers you have there...

I’m determined to live forever, or die trying. - Yossarian

tha fuck is this? algebra? geometry? fack, i wish i was still doing this shit.

daledude wrote: Well the definition of a geometric sequence is that a(n+1)/a(n)=r (parentheses are subscript). I would try plugging in all the possible answers and see which ones give you a constant for r.

Yeah (took me forever to understand that) it’s just a pain in the ass, literally, when extra variables start getting involved. Anything else and I could figure it out, that is a different story.
I mean, x-2/x+4? It depends on what X is, doesn’t it?

daledude wrote: For 33 I think you could do 20/r^2=8. That would give you r. Then multiply 8 by r to get K. Just remember that because you took the root of a square that your answer can be positive or negative.

Although when I worked it out this way it didn’t correspond to any of the answers you have there...

Yeah we were taught something like, T(n) = A(R)^n-1 (which would simplify to T(3) = 8(r)^2 then 20/8=R^2, same thing you got...)

EDIT: Think I just figured it out...
EDIT 2: Nevermind. >.>

This is really confusing because all our letters are different, lol.

I think I remember something like that from pre-calc, but now that I’m in calc 2 everything is written differently.

I’m determined to live forever, or die trying. - Yossarian

Lemme guess, you all got greek letters?

Tyreaus Dreacon wrote:

daledude wrote: For 33 I think you could do 20/r^2=8. That would give you r. Then multiply 8 by r to get K. Just remember that because you took the root of a square that your answer can be positive or negative.

Although when I worked it out this way it didn’t correspond to any of the answers you have there...

Yeah we were taught something like, T(n) = A(R)^n-1 (which would simplify to T(3) = 8(r)^2 then 20/8=R^2, same thing you got...)

EDIT: Think I just figured it out...
EDIT 2: Nevermind. >.>

Okay I see where that comes from. But you either typed out those MC answers wrong, or they don’t make any sense.

I’m determined to live forever, or die trying. - Yossarian

daledude wrote:

Tyreaus Dreacon wrote:

daledude wrote: For 33 I think you could do 20/r^2=8. That would give you r. Then multiply 8 by r to get K. Just remember that because you took the root of a square that your answer can be positive or negative.

Although when I worked it out this way it didn’t correspond to any of the answers you have there...

Yeah we were taught something like, T(n) = A(R)^n-1 (which would simplify to T(3) = 8(r)^2 then 20/8=R^2, same thing you got...)

EDIT: Think I just figured it out...
EDIT 2: Nevermind. >.>

Okay I see where that comes from. But you either typed out those MC answers wrong, or they don’t make any sense.

I double and triple checked. I got the answer to the one, so thanks for that.
But they’re typed out correctly. I can give answers if it helps:

27 was solved so that’s skipped:
D
D
A
-
B

Tyreaus Dreacon wrote: Lemme guess, you all got greek letters?

No just the sigma, which I believe you are already familiar with. And then next to the sigma is something like (2/7)^n (so we use n’s instead of K’s). Usually they go from n=1 or 0 to infinity. We deal mostly with the question of whether or not series converge. That is, if you add all the terms (an infinite amount) do you get a number or /-infinity.

I’m determined to live forever, or die trying. - Yossarian