Results 1 to 4 of 4

Math Help - Simple simultaneous equations problem

  1. #1
    Newbie
    Joined
    Nov 2009
    Posts
    3

    Simple simultaneous equations problem

    Just as a forewarning, I have no idea why I can't solve this and I feel unbelievably dumb.

    y = x^2
    y = 5x - 6

    Graphically it is seen that y = 4 and x = 2, but how do I solve it algebraically? Thanks in advance.
    Follow Math Help Forum on Facebook and Google+

  2. #2
    Member
    Joined
    Oct 2009
    Posts
    82
    If you want both equations to be true, you have that y = x^2, and that y = 5x - 6.

    In that case, x^2 = 5x - 6. Can you see why?

    Now you have a quadratic equation in x, which should be easy to solve.

    Also, don't forget, there are two points of intersection. You've found one; now you should be able to find the other.
    Follow Math Help Forum on Facebook and Google+

  3. #3
    Newbie I4talent's Avatar
    Joined
    Sep 2009
    Posts
    23
    Quote Originally Posted by Ruscour View Post
    Just as a forewarning, I have no idea why I can't solve this and I feel unbelievably dumb.

    y = x^2
    y = 5x - 6

    Graphically it is seen that y = 4 and x = 2, but how do I solve it algebraically? Thanks in advance.
    We have: y = x^2 and y = 5x-6.

    Let x^2 = 5x-6

    Then x^2-5x+6 = 0

    \implies (x-3)(x-2) = 0

    \implies x-3 = 0 or x-2 = 0

    \therefore x = 3 or x = 2.
    Follow Math Help Forum on Facebook and Google+

  4. #4
    Newbie
    Joined
    Nov 2009
    Posts
    3
    Why did I not think of a quadratic? Who knows.

    Thanks for your replies. It's interesting, as x = 3 and x = 2, the two graphs intercept each other at 2 different points, (3, 9) and (2, 4). Guess I just had a blonde moment.
    Follow Math Help Forum on Facebook and Google+

Similar Math Help Forum Discussions

  1. Simultaneous Equations Logarithms Problem
    Posted in the Algebra Forum
    Replies: 1
    Last Post: February 8th 2010, 06:01 AM
  2. simultaneous equations problem
    Posted in the Pre-Calculus Forum
    Replies: 5
    Last Post: January 27th 2010, 04:34 AM
  3. problem simultaneous equations
    Posted in the Math Topics Forum
    Replies: 4
    Last Post: June 30th 2008, 01:17 AM
  4. Replies: 3
    Last Post: April 23rd 2008, 09:24 PM
  5. simple simultaneous equations?
    Posted in the Algebra Forum
    Replies: 2
    Last Post: April 29th 2007, 07:34 AM

Search Tags


/mathhelpforum @mathhelpforum