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Slope-intercept, (determine, evaluate, domain) function, diff. quotient

  1. Feb 5, 2009 #1
    Domain Functions:

    f(x) = 4sq.root(1-x2), the 4 is on the outside

    f(s) = sq.root(s -1)/s-4

    f(x) = x-4/sq.root x

    I have absolutely no clue how to go about doing any of these, I take notes but I cannot piece it together; I have never felt so helpless at anything. This isn't homework I just want to know how to be able to do slope-intercept, determine a function, evaluate it, domain functions and difference quotients becaue I have a quiz on it tomorrow at 8:30 and I need to know how to at least start to solve them.
     
  2. jcsd
  3. Feb 6, 2009 #2

    symbolipoint

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    You asked for the domains of these functions according to what you expressed in pure text form:

    f(x) = 4[tex]\sqrt{1-2x}[/tex]

    f(x) = [tex]\frac{\sqrt{s - 1}}{s}[/tex] - 4

    f(x) = x -[tex]\frac{4}{\sqrt{x}}[/tex]

    Are those the functions you meant?
     
  4. Feb 6, 2009 #3
    Yeah, if you could just like direct to a website which explains these as a lesson or something, that would be great.
     
  5. Feb 6, 2009 #4

    HallsofIvy

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    The "domain" of a function, if nothing but the formula is given, is all values of x for which the formula can be evaluated. For most functions the only problems are:
    1) You can't divide by 0
    2) You can't take the square root of a negative number.

    Look at the last one:
    [tex]f(x)= x- \frac{4}{\sqrt{x}}[/tex]
    That first x is no problem- you could replace it with any number. But the other x is inside a square root- it can't be negative. Also it is in the denominator: [itex]\sqrt{0}[/itex] certainly exists, it is 0. But then you would be dividing by 0 so x also cannot be 0. In stating what the domain is you would reverse that: x cannot be negative or 0 so x can be any positive number. The domain is the set of all positive real numbers.
     
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