Results 1 to 4 of 4

Math Help - Final Exam Study Guide Help

  1. #1
    Newbie
    Joined
    Jul 2007
    Posts
    9

    Final Exam Study Guide Help

    I am working on my final exam study guide for college algebra and have a few I need help with.

    1 "Fill in the blank. Given that f(x) = -4x-2 and g(x)=x^2=9. (fog)(-9)= ?

    2 "Find the inverse of the funtion f(x)= 3x-5/6. Then Fill in the blank below. F^-1(x)= ?

    3 The intensity of illumination from a light source varies inversley with square of the distance from the source. Suppose that a reading lamp has an intensity of 5000 lumens at a distance of 4 feet.

    The intesnity of the lamp is how many lumens at a distance of 2 feet?

    The intensity of the lame is 300 lumens at a distnace of how many feet?
    Last edited by Ty Durdan; August 14th 2007 at 10:32 PM. Reason: MISTAKE
    Follow Math Help Forum on Facebook and Google+

  2. #2
    Grand Panjandrum
    Joined
    Nov 2005
    From
    someplace
    Posts
    14,972
    Thanks
    4
    Quote Originally Posted by Ty Durdan View Post
    I am working on my final exam study guide for college algebra and have a few I need help with.

    1 "Fill in the blank. Given that f(x) = -4x-2 and g(x)=x^2=9. (fog)(-9)= ?
    You shoud know that:

    (f \circ g)(x)=f(g(x))=f(x^2)=-4x^2-2

    RonL
    Follow Math Help Forum on Facebook and Google+

  3. #3
    Grand Panjandrum
    Joined
    Nov 2005
    From
    someplace
    Posts
    14,972
    Thanks
    4
    [quote=Ty Durdan;64733]2 "Find the inverse of the funtion f(x)= 3x-5/6. Then Fill in the blank below. F^-1(x)= ?

    If y=f(x)=3x-5/6, then x=y/3+5/18, so:

    [tex]f^-1(y)=y/3+5/18[tex]

    or rewriting using x as the variable:

    f^-1(x)=x/3+5/18

    RonL
    Follow Math Help Forum on Facebook and Google+

  4. #4
    Senior Member DivideBy0's Avatar
    Joined
    Mar 2007
    From
    Melbourne, Australia
    Posts
    432
    Quote Originally Posted by Ty Durdan View Post
    3 The intensity of illumination from a light source varies inversley with square of the distance from the source. Suppose that a reading lamp has an intensity of 5000 lumens at a distance of 4 feet.

    The intesnity of the lamp is how many lumens at a distance of 2 feet?

    The intensity of the lame is 300 lumens at a distnace of how many feet?
    Let I = intensity and D = distance, then

    I \propto \frac{1}{D^2}

    => I=\frac{k}{D^2}

    When I = 5000, D = 4, and we solve for k:

    5000=\frac{k}{4^2}

    k=80000

    => I=\frac{80000}{D^2}

    For the first question, D = 2:
    I=\frac{80000}{2^2}

    I=20000 lumens

    For the second, I = 300:
    300=\frac{80000}{D^2}

    D^2=\frac{80000}{300}

    D=\frac{20 \sqrt{6}}{3} feet (we obviously only need a positive solution)
    Follow Math Help Forum on Facebook and Google+

Similar Math Help Forum Discussions

  1. Study Guide for Actuarial Exams?
    Posted in the Business Math Forum
    Replies: 8
    Last Post: June 15th 2011, 07:50 PM
  2. Help on Study Guide
    Posted in the Discrete Math Forum
    Replies: 1
    Last Post: June 11th 2011, 11:13 AM
  3. Need help on study guide
    Posted in the Algebra Forum
    Replies: 2
    Last Post: May 3rd 2011, 10:30 AM
  4. Exam study guide help
    Posted in the Advanced Algebra Forum
    Replies: 2
    Last Post: December 15th 2009, 10:59 PM
  5. Study Guide Help
    Posted in the Advanced Statistics Forum
    Replies: 0
    Last Post: December 5th 2008, 10:59 PM

Search Tags


/mathhelpforum @mathhelpforum