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Thread: what is the value of x?

  1. #1
    rcs
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    what is the value of x?

    Find the value of x (either odd or even)..

    5x^7 + 3x^4 = 241
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    rcs
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    Re: what is the value of x?

    Quote Originally Posted by rcs View Post
    Find the value of x (either odd or even)..

    5x^7 + 3x^4 = 241

    because if x = 1

    then 5(1)^7 + 3(1)^4 = 8 which is not equal to 241

    if x = 2

    then
    5(2)^7 + 3(2)^4 = 688 which is not equal to 241

    What shall i do with this?
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  3. #3
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    Re: what is the value of x?

    your equation does not have an integer solution.

    let $f(x)=5x^7+3x^4-241$

    note $f(1)=-233$ and $f(2)=447$ ... since the function is continuous, there exists a value of $x$ in the interval $(1,2)$ where $f(x) = 0$

    attached is a graph showing that single real zero
    Attached Thumbnails Attached Thumbnails what is the value of x?-7th_deg_zero.png  
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    Re: what is the value of x?

    Quote Originally Posted by rcs View Post
    Find the value of x (either odd or even)..
    5x^7 + 3x^4 = 241
    Go here and enter your equation:
    Wolfram|Alpha: Computational Knowledge Engine
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    Re: what is the value of x?

    Quote Originally Posted by rcs View Post
    Find the value of x (either odd or even)..

    5x^7 + 3x^4 = 241
    The reason I know your equation has no solutions in integers is A) if x is an odd integer,
    then the left-hand side is even because is it the sum of two odd numbers, and B) if x
    is an even integer, then the left-hand side is even because is it the sum of two even
    numbers.

    No specific values of x need to be substituted to do the problem. The corresponding
    graph of f(x) = 5x^7 + 3x^4 need not be checked.
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