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Math Help - Quick question on why I got something wrong

  1. #1
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    Quick question on why I got something wrong

    I was given \int^4_0 f(x)\,dx = 4

    I was asked to evaluate the following:
    \int^4_0 (3*f(x)+1)\,dx

    What I simply did was took 3*4+1=13 and I was marked down a point. How is this incorrect? I'm sure it's something stupid I am not seeing but I can't seem figure it out!
    Thanks
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  2. #2
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    Opalg's Avatar
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    Re: Quick question on why I got something wrong

    Quote Originally Posted by NeedDirection View Post
    I was given \int^4_0 f(x)\,dx = 4

    I was asked to evaluate the following:
    \int^4_0 (3*f(x)+1)\,dx

    What I simply did was took 3*4+1=13 and I was marked down a point. How is this incorrect? I'm sure it's something stupid I am not seeing but I can't seem figure it out!
    Thanks
    What is \int_0^41\,dx ?
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  3. #3
    MHF Contributor FernandoRevilla's Avatar
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    Re: Quick question on why I got something wrong

    Quote Originally Posted by NeedDirection View Post
    What I simply did was took 3*4+1=13 and I was marked down a point. How is this incorrect? I'm sure it's something stupid I am not seeing but I can't seem figure it out!
    The solution is not 13 :

    \int_0^4(3f(x)+1)dx=\int_0^43f(x)dx+\int_0^41dx=

    3\int_0^4 f(x)+[x]_0^4=3\cdot 4+(4-0)=16

    Edited: Sorry, I didn't see Opalg's post.
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  4. #4
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    Re: Quick question on why I got something wrong

    Just as I expected, something simple I couldn't see!
    Thanks guy's!
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