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Math Help - expanding brackets

  1. #1
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    expanding brackets

    Hi what is (3x + 1/x)^2 ???????
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  2. #2
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    Quote Originally Posted by wolfhound View Post
    Hi what is (3x + 1/x)^2 ???????
    HINT: (a + b)^2 = (a + b) times (a + b)
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  3. #3
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    Quote Originally Posted by Wilmer View Post
    HINT: (a + b)^2 = (a + b) times (a + b)
    I know that
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  4. #4
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    Hi!

    In addition to Wilmer's post

    One should lnow the binimial theorems

    (a+b)^2 = a^2 + 2ab + b^2

    (a-b)^2 = a^2 - 2ab + b^2

    (a+b)(a-b) = a^2-b^2

    In the example it is a = 3x and b = 1/x

    Can you solve it now?

    Edit

    Quote Originally Posted by wolfhound View Post
    I know that
    Okay, here is the solution

    (3x)^2+2*(3x)*(1/x)+(1/x)^2

    = 9x^2+\frac{6x}{x} + \frac{1^2}{x^2}

    = 9x^2 +6 + \frac{1}{x^2}
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  5. #5
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    I know all that pascals triangle stuff ,what I dont understand is what becomes of 3x when its multiplied by 1/x?? or 1/x x 1/x?
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  6. #6
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    Thumbs up

    Okay, here is the solution

    (3x)^2+2*(3x)*(1/x)+(1/x)^2

    = 9x^2+\frac{6x}{x} + \frac{1^2}{x^2}

    = 9x^2 +6 + \frac{1}{x^2}[/QUOTE]

    thanks
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  7. #7
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    Quote Originally Posted by wolfhound View Post
    I know all that pascals triangle stuff ,what I dont understand is what becomes of 3x when its multiplied by 1/x?? or 1/x x 1/x?
    (3x)(\frac{1}{x})= \frac{3x}{x}= 3

    (\frac{1}{x})(\frac{1}{x})= \frac{1}{x^2}
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