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Thread: Please help me on these questions

  1. #1
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    Please help me on these questions

    Hi I'm new here and I need some help please.

    1. S=3/1-r if r= -3/4 , S=?

    2. t=16(-1/2) ^x-1 if n=8

    3. T= -1/2(2)^n-1 if t=-32 , n=?

    4. write the quadratic equation whose roots are 2/3 and -1

    5.What are the restrictions on the graph of y= x+2/ (x-a)(bx-1)

    6. How many solutions are there for the follow non-linear system?

    y= 2/x and y= (x+1)^2 -2

    If anyone could me with these it would be great! Thanks a lot!
    Last edited by Dida; Sep 15th 2009 at 09:19 PM. Reason: Missed a question
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  2. #2
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    There are quite a few questions here. I believe the moderation team likes members to limit the number of questions to around 3 per post. However, here is assistance with the first four:

    1. S=3/1-r if r= -3/4 , S=?
    $\displaystyle S=\frac{3}{1}-r$

    By subbing in the value of r:
    $\displaystyle S=\frac{3}{1}+\frac{3}{4}$

    Can you solve it from there?


    2. $\displaystyle t=16(-1/2)^x-1$
    Actually, this question makes no sense. No n value exists in the original equation, so you're unable to substitute n=8 anywhere.


    3.
    $\displaystyle T= -1/2(2)^n-1$ - I will assume the -1 is not part of the exponent.
    $\displaystyle -32= -1/2(2)^n-1$
    $\displaystyle -31= -1/2(2)^n$
    $\displaystyle 62=(2)^n$
    $\displaystyle ln(62)=n*ln(2)$

    Can you take it from there?

    4. write the quadratic equation whose roots are 2/3 and -1
    By using null factor rule:
    $\displaystyle \frac{2}{3}=x$
    $\displaystyle 3x-2=0$

    $\displaystyle -1=x$
    $\displaystyle x + 1=0$

    Therefore,
    $\displaystyle 0=(x+1)(3x-2)$

    Can you solve it from there?
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  3. #3
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    Thanks for the help, but for #1-3 I'll try to explain the question better.

    1. S= 3
    ________ if r= -3/4 , S=?
    1-r

    2. the x is the n sorry, so its like:

    t= 16(-1/2)^n-1 (yes the -1 is part of n)

    3. the -1 is part of the exponent, but that wouldn't make a difference right? since your using ln anyway. Couldn't I use log?

    4. I get 4 but that's the answer right? Because you cant really do anything more to it.

    Thanks again!
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  4. #4
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    Bump! someone please help lol I need to finish this tonight.
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  5. #5
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    1. S= 3
    ________ if r= -3/4 , S=?
    1-r

    $\displaystyle S=\frac{3}{1-r}$
    $\displaystyle S=\frac{3}{1-(3/4)}$
    $\displaystyle S=\frac{3}{.25}$.... Can you solve that?

    2. $\displaystyle t=16(-1/2)^{(n-1)}$
    $\displaystyle t=16(-1/2)^{(8-1)}$
    $\displaystyle t=16(-1/2)^7$
    $\displaystyle t=16 \times -\frac{1}{128}$.. can you finish it?

    3. $\displaystyle T= -1/2(2)^{(n-1)}$
    $\displaystyle -32= -1/2(2)^{(n-1)}$
    $\displaystyle 64= (2)^{(n-1)}$
    $\displaystyle 2^6= (2)^{(n-1)}$
    $\displaystyle 6= n-1$... sooo n=??

    4. It depends what form you want the answer in. I'd suggest expanding out into 'standard form'.
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