Results 1 to 5 of 5

Math Help - Finding a Quadratic Equation from Mulitple Points

  1. #1
    Newbie
    Joined
    Mar 2009
    From
    Vancouver
    Posts
    18

    Finding a Quadratic Equation from Mulitple Points

    I know their are quite a few of these questions on the net and I have looked at them, but I havent really been able to properly understand how they actually work.

    I have to find what x when y=.11, so im guessing that I need to find the quadratic equation, right???
    NOTE: Im not 100% sure this is a quadratic equation. If it isn't, any suggestions on how to solve it.

    x y

    0 16
    1 8
    2 4
    3 2
    4 1
    5 0.5
    6 0.25
    7 0.125
    8 0.0625
    Follow Math Help Forum on Facebook and Google+

  2. #2
    Member
    Joined
    Aug 2009
    Posts
    125
    Hi,
    It's not a quadratic function, it is rather y=2^{4-x}.
    Follow Math Help Forum on Facebook and Google+

  3. #3
    Newbie
    Joined
    Mar 2009
    From
    Vancouver
    Posts
    18
    Can I use this to solve my problem???
    Follow Math Help Forum on Facebook and Google+

  4. #4
    Member
    Joined
    Aug 2009
    Posts
    125
    yes, take logarithm of both sides to express x:
    \ln y=\ln (2^{4-x}) = (4-x)\ln2, so x=4-\frac{\ln y}{\ln 2}.

    I don't know what ".11" is, never seen it. Can you explain pls?
    Follow Math Help Forum on Facebook and Google+

  5. #5
    Newbie
    Joined
    Mar 2009
    From
    Vancouver
    Posts
    18
    Sorry. Its part of a word problem where I have to find the age (in carbon-14 half lives) of a sample with a rate of disintergration of C-14 of .11 disintergrations/min/gram. I ve been given the first the first 3 numbers of each variable and I used Excel to copy the formula.

    Half Life Disintergration rate
    0 16
    1 8
    2 4
    (Note 1 C-14 Half-Life = 5730 Years before present)
    Follow Math Help Forum on Facebook and Google+

Similar Math Help Forum Discussions

  1. Finding the equation given 3 points
    Posted in the Algebra Forum
    Replies: 4
    Last Post: November 12th 2011, 09:02 AM
  2. [SOLVED] Finding the equation of a plane given three points.
    Posted in the Calculus Forum
    Replies: 1
    Last Post: February 13th 2011, 04:26 PM
  3. Replies: 11
    Last Post: May 6th 2010, 11:59 AM
  4. finding quadratic equation, when given 3 points
    Posted in the Pre-Calculus Forum
    Replies: 3
    Last Post: March 21st 2009, 02:51 AM
  5. Replies: 1
    Last Post: November 27th 2007, 11:07 PM

Search Tags


/mathhelpforum @mathhelpforum