Results 1 to 5 of 5

Math Help - [SOLVED] Equation of 2 graphs

  1. #1
    Newbie
    Joined
    Apr 2010
    Posts
    12

    Question [SOLVED] Equation of 2 graphs

    Hi everyone I have a maths question as follows:

    Plot the graphs of y=x^2+x-1 and y=x+1 as accurately as possible on the same axis using value of x from -4 to +4

    Write down an equation for the values of x where the graphs meet and solve this equation. Check and show the solution on the graph.

    OK so I have drawn it by hand but to illustrate I plotted it in excel for you all to see here:



    Can anyone tell me how to find out the equation I need to answer this question please?

    Thanks for your time - James
    Follow Math Help Forum on Facebook and Google+

  2. #2
    Super Member bigwave's Avatar
    Joined
    Nov 2009
    From
    honolulu
    Posts
    580

    set them equal to each other

     y=x^2+x-1 and y=x+1

    since these equations both =y then set them equal to each other

    so x^2 + x -1 = x+1 then solve for x to get the x values

    thus

    x^2 = 2  \rightarrow x = \pm\sqrt{2}

    Last edited by bigwave; June 2nd 2010 at 10:09 AM. Reason: spelling, added graph
    Follow Math Help Forum on Facebook and Google+

  3. #3
    Newbie
    Joined
    Apr 2010
    Posts
    12
    Quote Originally Posted by bigwave View Post
     y=x^2+x-1 and y=x+1

    since these equations both =y then set them equal to each other

    so x^2 + x -1 = x+1 then solve for x to get the x values

    thus

    x^2 = 2  \rightarrow x = \pm\sqrt{2}
    So how did you get to x^2=2 ?

    +1 each side then subtract x's ?
    Follow Math Help Forum on Facebook and Google+

  4. #4
    Super Member bigwave's Avatar
    Joined
    Nov 2009
    From
    honolulu
    Posts
    580
    Quote Originally Posted by JamesC1705 View Post
    So how did you get to x^2=2 ?

    +1 each side then subtract x's ?
     x^2 + x -1 = x +1

    add 1 to both sides then

     x^2 + x = x + 2

    subtract x from both sides then

     x^2 = 2

    thus

     <br />
x = \pm\sqrt{2}<br />
    Follow Math Help Forum on Facebook and Google+

  5. #5
    Newbie
    Joined
    Apr 2010
    Posts
    12
    Ok thanks for all your help

    Just have to write it all out now

    Next up is an equation of a straight line graph but I think I can research and figure out the answer but you never know haha watch this space
    Follow Math Help Forum on Facebook and Google+

Similar Math Help Forum Discussions

  1. [SOLVED] Eulerian graphs
    Posted in the Discrete Math Forum
    Replies: 3
    Last Post: May 13th 2010, 10:40 AM
  2. [SOLVED] Different Graphs of Sinx and Cosx
    Posted in the Trigonometry Forum
    Replies: 4
    Last Post: May 7th 2010, 07:38 AM
  3. [SOLVED] Volume of graphs
    Posted in the Calculus Forum
    Replies: 3
    Last Post: April 20th 2010, 05:36 PM
  4. [SOLVED] Trig Function Graphs
    Posted in the Trigonometry Forum
    Replies: 4
    Last Post: February 5th 2009, 05:53 PM
  5. [SOLVED] Polar graphs
    Posted in the Pre-Calculus Forum
    Replies: 4
    Last Post: June 14th 2008, 03:29 PM

Search Tags


/mathhelpforum @mathhelpforum