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Math Help - Find limit at infinity

  1. #1
    DBA
    DBA is offline
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    Find limit at infinity

    lim x -> - infinity 2x^3 / x+9

    I do not understand how to solve a problem like this.

    Somehow I need to change it to

    2x^2 / 1 + (9/x^3) --> I do not know ho to get here.

    and I do not know how to find the answer.

    Please help and please explain the steps to get to the solution.
    Thanks
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  2. #2
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    a common method to solving these kind of limits is to divide the top and bottom of the fraction by the highest power of x in the denominator. since the highest power in the denominator is x (x^1), divide the top and bottom by x so that you get 2x^2 / (1 + 9/x). if you now take the limit as x approaches infinite, the 9/x goes to 0 and the 2x^2 goes to infinite. so you get infinite / 1 which is infinite which means the limit does not exist.
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