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Thread: Make 'N' the Subject

  1. #1

    Make 'N' the Subject

    Hey, before I start I just want to say that yes I am new, this is my first ever post but I've tried to look for help on questions in this book which ask to make 'N' or 'X' the subject so I decided to look at a maths forum and bam, I'm here.
    I need to really study at this seeing as I'm not very confident on maths and am really looking for a way of helping me with this question with a way of acutally teaching me of how you got the answer so I can apply it to most other questions. Here it is.

    Make n the subject,

    T=n^2 + 5

    (by the way, N is squared, that litle ^2 is just what I think refers to squaring).

    If anyone could please give me just 5 minutes of time, I would be VERY grateful for this. Thanks .
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  2. #2
    Super Member

    May 2006
    Lexington, MA (USA)
    Hello, GreenStreet!

    Solve for $\displaystyle n\!:\;\;T\;=\;n^2 + 5$

    We have: .$\displaystyle n^2 + 5 \;=\;T$

    Subtract 5 from both sides: . $\displaystyle n^2\;=\;T-5$

    Take the square root: . $\displaystyle n \;=\;\pm\sqrt{T-5} $

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  3. #3
    Feb 2008

    Make N the subject

    You are correct to assume ^ means squared.
    Taking T=N^2 +5
    There is no harm in rewriting this as
    N^2 + 5 =T
    This at least gives you N where you would like it to be, and has no effect on the equation.
    What you want is to get N on its own so you want to get rid of the 5
    If you take 5 away from both sides of the equation they will still be balanced and you get
    N^2 +5 -5 = T-5
    This will simplify to
    N^2 = T-5
    As you only want N and not N squared you need to "undo" the squaring. i.e. Find the square root. Again what you do to one side of an equation you must also do to the other, so you get
    Square root(N^2) = Square Root (T-5)
    Which simplifies to
    N= Square Root(T-5) (Square root of something squared gives you the original value before squaring)

    You can write square root as something raised to the power 1/2
    N = (T-5)^1/2

    Hope this helps
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