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Homework Help: Dumb Cal question

  1. Feb 6, 2005 #1
    Let f(x) = 8x^2 -7x +5. Then the quotient f(10 + h)/h - f(10)/h can be simplified to ah + b when a = ? and b = ?

    I'm completly stumped on this one...I'm not even sure what they're asking!!!

    Is it saying that when x=10, the rate of change is given by the function ah + b?

    If so, why can't i just plug in the 10 into the derivative 16x -7 to find the slope of the tangeant line and find the equation that way ?
     
  2. jcsd
  3. Feb 6, 2005 #2

    dextercioby

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    They'r asking you to do that,no calculus involved whatsoever,just simple algebra
    [tex] \frac{8(10+h)^{2}-7(10+h)+5-8(10)^{2}+7(10)-5}{h} [/tex]

    Daniel.
     
  4. Feb 6, 2005 #3
    OHHHHHH

    I tried that but forgot to inverse the symbols within f(x) brackets...haha :blushing:

    That was helpful...are you daniel jackson of stargate?
     
  5. Feb 6, 2005 #4

    dextercioby

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    Nope,i'm the one & only Daniel Ciobotu from Craiova/Romania... :smile:

    Daniel.
     
  6. Feb 6, 2005 #5
    Might as well continue this thread with some more newbie questions

    I'm trying my hand at some harder stuff that's not part of my homework.

    How would I find the derivative of 5x + 3*sqrt of x ? There are two x variables so 2 h differences for each?
     
  7. Feb 6, 2005 #6

    dextercioby

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    Do you know the rules of differentiation??E.g.
    [tex] (x^{n})'=...? [/tex]

    Daniel.

    P.S."n" is real...
     
  8. Feb 8, 2005 #7
    n * x^n-1 ?

    That's about all i know ;D
     
  9. Feb 8, 2005 #8

    dextercioby

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    Well,that's good enough.Apply that formula for your case.

    Daniel.
     
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