Question

Graphing exponential growth?

Answer 1

If I could get help on this that would be great!
http://imgur.com/iWG1aiE

I would appreciate it so much!

I figured a) and b) but I would like help on figuring out c)!
a) tn = 100000(1.04)^n-1
b) I will graph it
c) ?? Help would be appreciated!

Answer 2

Is ur equation for a right? I think it's just n, not n-1

Answer 3

@nikato - it probably just is n, not n-1. sorry!

Answer 4

Ok. Now with ur equation from a, plug in 130000 for tn and solve for n

Answer 5

@nikato - Thanks, I get that, but how would I solve for n? Do i take the square root of everything? This is where I am stuck.

Answer 6

I think it'll be better using logs

Answer 7

@nikato - How would I do that? Could you please provide an example?

Answer 8

Becuz u'll have 130000=100000(1.04)^n
Divide both sides by 100000

Answer 9

Then once u do that change it to log.

So if u have y=b^x
Log b (y)=x

Answer 10

Then use the change of base
http://www.purplemath.com/modules/logrules5.htm

Answer 11

1.3 =(1.04)^n, is that right? So then it would be Log 10.4(1.3) = x?
The answer is supposed to be 7, or 2012. I just want to know how to work it. :(

Answer 12

@nikato

Answer 13

So log 1.04 (1.3)=n

With the change of base rule, u get

Log 1.3
---------
Log 1.04

Plug that in ur calculator to find n

Answer 14

I got 1.25, is that right?

Answer 15

@nikato

Answer 16

No, u forgot the log

Answer 17

log 1.25? But we are supposed to get a numerical value. The answer is supposedly 7 but I don't know how to get 7.

Answer 18

R u using a calculator?

Answer 19

If u plug in log(1.3)/ log(1.04) into ur calculator, u'll get 6.689.... Which u can round off to 7

Answer 20

@nikato
Sorry my mistake. I see where I did this wrong. Thanks so much for the help I really appreciate it!
Also, did I graph this function right? http://imgur.com/nu0rOqJ

Answer 21

Ok. So if u find n=7. 2005+7=2012.

And I don't think it's right. U graphed a linear equation. Ur graph should have a curve becuz it's exponential
http://regentsprep.org/regents/math/algebra/ae7/expdecayl.htm

Answer 22

@nikato thanks so much!
It would be exponential decay, right? Since a > 0 and b between 0 and 1?

Answer 23

Nevermind it's 1.04 so it would be growth. Silly me. :p

Answer 24

Growth also becuz in ur problem, it stated increase, not decrease

Answer 25

@nikato, one last favor.. haha sorry
Could you help me out on how to graph it? Would I start at one? The rules say that for this case, each time x is increased by 100000, y increases by a factor of 1.04... Would it be the other way around? Because x only goes 1 - 10 :(

Answer 26

No, that is incorrect. X does not increase by 100000, this # is ur initial #, also known as ur y-intercept or the y when x=0. For the rest of the points, I'll will just plug in different x to find y and then graph those points

Answer 27

@nikato - Thanks so much! I really appreciate the help!

Answer 28

Yea, no problem. Glad u understand this now