Results 1 to 6 of 6

Math Help - Exponential Equation??

  1. #1
    Newbie
    Joined
    Nov 2010
    Posts
    3

    Exponential Equation??

    Came across an exponential equation that I am having a hard time solving. If anyone can walk me through this it would be appreciated...

    2^x - 4x + 1 = 0

    Problem says use the calculator to obtain a decimal approximation for the solution.

    Thanks in advance.
    Follow Math Help Forum on Facebook and Google+

  2. #2
    MHF Contributor

    Joined
    Aug 2006
    Posts
    18,605
    Thanks
    1574
    Awards
    1
    You posted this in the basic algebra forum.
    Therefore, I think that you are meant to graph the expression.
    See where the zeros would be and then ‘zoom in’ on them.
    It appears that it has two roots between 0 & 5.
    Follow Math Help Forum on Facebook and Google+

  3. #3
    Newbie
    Joined
    Nov 2010
    Posts
    3
    maybe I posted in the wrong section. I believe I have to somehow use log or ln in this problem, as that is the chapter we are currently on. If it had just been 2^x + 1 i could do. But that -4x throws me off.

    The multiple choice answers are A. .639, 3.847 B. .639 C. 14.387 D. 3.847
    Follow Math Help Forum on Facebook and Google+

  4. #4
    MHF Contributor

    Joined
    Aug 2006
    Posts
    18,605
    Thanks
    1574
    Awards
    1
    Quote Originally Posted by PhilipL View Post
    maybe I posted in the wrong section. I believe I have to somehow use log or ln in this problem, as that is the chapter we are currently on. If it had just been 2^x + 1 i could do. But that -4x throws me off.
    The multiple choice answers are A. .639, 3.847 B. .639 C. 14.387 D. 3.847
    The answer is A.
    Using zoom I found that answer.

    If you know calculus, then Newton's Method gives the same answer.
    Follow Math Help Forum on Facebook and Google+

  5. #5
    MHF Contributor FernandoRevilla's Avatar
    Joined
    Nov 2010
    From
    Madrid, Spain
    Posts
    2,162
    Thanks
    45
    Quote Originally Posted by PhilipL View Post
    Problem says use the calculator to obtain a decimal approximation for the solution.
    The function f(x)=2^x-4x+1 is continuous on \mathbb{R}. Besides f(0)=2>0 , f(1)=-1<0, f(3)=-3<0 and f(4)=1>0. According to Bolzano's Theorem there are two solutions c_1\in (0,1) and c_2\in (3,4) for the equation f(x)=0. It is easy to prove that the equation has not more solutions.

    Now using the calculator, you can try f(0'1),\;f(0'9),\ldots etc.

    Regards.

    Fernando Revilla

    Edited: Sorry, I didn't see the previous answers.
    Follow Math Help Forum on Facebook and Google+

  6. #6
    Newbie
    Joined
    Nov 2010
    Posts
    3
    kinda feel dumb now. I was just overthinking the question. But thanks!
    Follow Math Help Forum on Facebook and Google+

Similar Math Help Forum Discussions

  1. exponential equation
    Posted in the Pre-Calculus Forum
    Replies: 4
    Last Post: February 6th 2010, 10:46 AM
  2. Exponential Equation
    Posted in the Pre-Calculus Forum
    Replies: 0
    Last Post: October 25th 2009, 12:08 PM
  3. Exponential equation
    Posted in the Algebra Forum
    Replies: 4
    Last Post: August 2nd 2009, 05:13 AM
  4. Exponential Equation
    Posted in the Algebra Forum
    Replies: 8
    Last Post: January 13th 2009, 11:21 AM
  5. exponential equation
    Posted in the Algebra Forum
    Replies: 2
    Last Post: November 5th 2008, 12:13 AM

Search Tags


/mathhelpforum @mathhelpforum