Results 1 to 5 of 5

Math Help - average rate of change? help

  1. #1
    Member
    Joined
    Jan 2009
    From
    USA
    Posts
    123

    average rate of change? help

    average rate of change?

    Problem:
    Find the average rate of change of the function f(x)=-3(x^2)-x from x1=5 to x2=6. The formula for average rate of change from a to b is (f(b)-f(a))/b-a

    a)-1/6
    b)-34
    c)-2
    d)1/34
    e)1/2

    help please!
    Follow Math Help Forum on Facebook and Google+

  2. #2
    Senior Member mollymcf2009's Avatar
    Joined
    Jan 2009
    From
    Charleston, SC
    Posts
    490
    Awards
    1
    Hello!

    All the information you need is given to you. You just need to plug it all in.

    You are given your two x values (5 & 6) now, to find f(5) & f(6) just plug them into the function and find your y values.

    f(x) = y

    When you see f(x) that means that you are solving for y in terms of x

    If you are given an x value and a function f(x), you can plug the x value into every single x in the function and it will calculate the y value associated with that x value. So f(5) = -80 See if you can go from there!
    Good Luck!
    Follow Math Help Forum on Facebook and Google+

  3. #3
    Member
    Joined
    Jan 2009
    From
    USA
    Posts
    123
    Quote Originally Posted by mollymcf2009 View Post
    Hello!

    All the information you need is given to you. You just need to plug it all in.

    You are given your two x values (5 & 6) now, to find f(5) & f(6) just plug them into the function and find your y values.

    f(x) = y

    When you see f(x) that means that you are solving for y in terms of x

    If you are given an x value and a function f(x), you can plug the x value into every single x in the function and it will calculate the y value associated with that x value. So f(5) = -80 See if you can go from there!
    Good Luck!

    huh? i think i am more confused than before...........
    Follow Math Help Forum on Facebook and Google+

  4. #4
    Senior Member mollymcf2009's Avatar
    Joined
    Jan 2009
    From
    Charleston, SC
    Posts
    490
    Awards
    1
    Ok, no problem. Let me try to explain it another way.

    The average rate of change of a function is also known as the slope. You know what slope is right?

    slope = \frac{y_2-y_1}{x_2-x_1}

    OR,

    slope = \frac{change-in-y-values}{change-in-x-values}

    OR,

    slope = \frac{f(b)-f(a)}{b-a}

    b & a are just x coordinates somewhere on your function

    f(b) & f(a) are the y values associated with those x values.

    Since you are given the x values of the coordinates on the function, just plug those into your function to give you the y values.

    All that f(x) means is y. f(x) is the function y, evaluated at an x value.

    So for example:

     f(x) = 2x^2 - 6x + 3

    Find f(2).

    f(2) = 2(2)^2 - 6(2) + 3

    In calculus,

    The average rate of change of a function is the slope of the of the secant line between two points somewhere on the graph. A secant line is a line that goes through the graph of a function in two places. It calculates the average of the slopes of all the tangent line to the function between those two given points.

    Hope that clarifies better for you
    Last edited by mollymcf2009; January 29th 2009 at 10:21 PM.
    Follow Math Help Forum on Facebook and Google+

  5. #5
    Member
    Joined
    Jan 2009
    From
    USA
    Posts
    123
    yea i got it now.
    thank you so much
    Follow Math Help Forum on Facebook and Google+

Similar Math Help Forum Discussions

  1. Average rate of change!
    Posted in the Pre-Calculus Forum
    Replies: 4
    Last Post: January 27th 2010, 08:32 PM
  2. Average Rate of Change
    Posted in the Pre-Calculus Forum
    Replies: 1
    Last Post: October 28th 2009, 02:54 PM
  3. average rate of change
    Posted in the Pre-Calculus Forum
    Replies: 2
    Last Post: September 27th 2009, 10:22 AM
  4. Average Rate of Change
    Posted in the Pre-Calculus Forum
    Replies: 2
    Last Post: October 27th 2008, 09:39 PM
  5. average rate of change
    Posted in the Pre-Calculus Forum
    Replies: 3
    Last Post: August 16th 2008, 10:55 AM

Search Tags


/mathhelpforum @mathhelpforum