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Math Help - limit & derivative

  1. #1
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    limit & derivative

    hey guys having trouble with this question. any help?

    Use f '(x) = lim h->0 f(x + h) - f(x)/h

    to find dy/dx when y = 3x + 4.

    much appreciated!
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  2. #2
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    Quote Originally Posted by jvignacio View Post
    hey guys having trouble with this question. any help?

    Use f '(x) = lim h->0 f(x + h) - f(x)/h

    to find dy/dx when y = 3x + 4.

    much appreciated!
    f(x) = 3x + 4.

    f(x + h) = 3(x + h) + 4.

    f(x + h) - f(x) = 3h.


    \frac{f(x+h)-f(x)}{h} = 3.


    \lim_{h \rightarrow 0} \frac{f(x+h)-f(x)}{h} = \lim_{h \rightarrow 0} 3 = 3.
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  3. #3
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    Quote Originally Posted by mr fantastic View Post
    f(x) = 3x + 4.

    f(x + h) = 3(x + h) + 4.

    f(x + h) - f(x) = 3h.


    \frac{f(x+h)-f(x)}{h} = 3.


    \lim_{h \rightarrow 0} \frac{f(x+h)-f(x)}{h} = \lim_{h \rightarrow 0} 3 = 3.
    haha any way of explaining what u did ??? so i can do the others myself.
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  4. #4
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    Quote Originally Posted by jvignacio View Post
    haha any way of explaining what u did ??? so i can do the others myself.
    That's about as plain as it will ever get! What don't you understand?
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  5. #5
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    Quote Originally Posted by mr fantastic View Post
    That's about as plain as it will ever get! What don't you understand?
    actually its okay. i understand now. thank u
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