Results 1 to 5 of 5

Math Help - quadradic

  1. #1
    Newbie
    Joined
    Jan 2008
    Posts
    14

    Unhappy quadradic

    sole the simultaneous equations

    y=x-4
    2x^2-xy=8

    giving your answers in the form a plus or minus b root3 , where a and b are integers
    Follow Math Help Forum on Facebook and Google+

  2. #2
    Junior Member
    Joined
    Mar 2008
    Posts
    49
    Hello

    Substitute to eleminate y.

    2x^2 -x(x - 4) = 8

    Now solve for x.
    Follow Math Help Forum on Facebook and Google+

  3. #3
    Moo
    Moo is offline
    A Cute Angle Moo's Avatar
    Joined
    Mar 2008
    From
    P(I'm here)=1/3, P(I'm there)=t+1/3
    Posts
    5,618
    Thanks
    6
    Hello,

    In the second equation, replace y by x-4

    -> 2x-x(x-4)=8

    --> 2x-x+4x=8

    ---> x+4x-8=0

    Calculate the discriminant, which is 4+4*8 = 48 = 16*3 = (4 root 3)

    And then, the solutions...
    Follow Math Help Forum on Facebook and Google+

  4. #4
    Newbie
    Joined
    Jan 2008
    Posts
    14
    Quote Originally Posted by Moo View Post
    Hello,

    In the second equation, replace y by x-4

    -> 2x-x(x-4)=8

    --> 2x-x+4x=8

    ---> x+4x-8=0

    Calculate the discriminant, which is 4+4*8 = 48 = 16*3 = (4 root 3)

    And then, the solutions...
    i dont know how to solve x+4x-8=0
    Follow Math Help Forum on Facebook and Google+

  5. #5
    Junior Member
    Joined
    Mar 2008
    Posts
    49
    One way, complete the square.

    2x^2 - x^2 + 4x = 8

    x^2 + 4x = 8

    (x + 2)^2 - 4 = 8

    (x + 2)^2 = 12

    x + 2 = +/- root 12

    x = -2 +/- 2 root 3
    Follow Math Help Forum on Facebook and Google+

Similar Math Help Forum Discussions

  1. quadradic
    Posted in the Algebra Forum
    Replies: 1
    Last Post: September 20th 2008, 11:10 AM
  2. quadradic
    Posted in the Algebra Forum
    Replies: 4
    Last Post: September 18th 2008, 06:43 PM
  3. fit to quadradic
    Posted in the Pre-Calculus Forum
    Replies: 2
    Last Post: May 10th 2008, 10:10 PM
  4. quadradic
    Posted in the Algebra Forum
    Replies: 1
    Last Post: March 29th 2008, 10:04 PM
  5. quadradic
    Posted in the Algebra Forum
    Replies: 1
    Last Post: January 15th 2008, 02:45 PM

Search Tags


/mathhelpforum @mathhelpforum