Results 1 to 3 of 3

Math Help - simultaneous equations

  1. #1
    Newbie
    Joined
    Jan 2009
    Posts
    8

    Exclamation simultaneous equations

    i got given this question

    solve the following simultaneous equations showing all your working out substitute your answers to check them at the end

    y= 20x - 15

    y + 30x = 60

    can someonbody tell me if how to do this question and wheter it means work each individual question out or both of them
    Follow Math Help Forum on Facebook and Google+

  2. #2
    Senior Member vincisonfire's Avatar
    Joined
    Oct 2008
    From
    Sainte-Flavie
    Posts
    469
    Thanks
    2
    Awards
    1
    You replace y in the second equation
    y + 30x = 20x - 15 + 30x = 50x - 15 = 60
     50x  = 75  \implies x = \frac{3}{2}
    Follow Math Help Forum on Facebook and Google+

  3. #3
    Member TheMasterMind's Avatar
    Joined
    Dec 2008
    Posts
    155
    Quote Originally Posted by jm16 View Post
    i got given this question

    solve the following simultaneous equations showing all your working out substitute your answers to check them at the end

    y= 20x - 15

    y + 30x = 60

    can someonbody tell me if how to do this question and wheter it means work each individual question out or both of them

    (1)y= 20x - 15

    (2)y + 30x = 60

    y in (1) is isolated, therefore use the method of substitution to solve(plug the value of y in (1) to y in (2)

    20x-15+30x=60

    50x=75

    x=1.5

    substitute this x value back into (2) to solve for y

    y+30(1.5)=60

    y+45=60

    y=15

    Checking

    (1)

    15=20(1.5)-15

    15=15

    (2)

    15+30(1.5)=60

    60=60

    \therefore the lines intersect at (1.5,15)
    Follow Math Help Forum on Facebook and Google+

Similar Math Help Forum Discussions

  1. Simultaneous Equations 4 variables, 4 equations
    Posted in the Pre-Calculus Forum
    Replies: 3
    Last Post: December 7th 2011, 04:06 PM
  2. simultaneous equations
    Posted in the Algebra Forum
    Replies: 11
    Last Post: September 4th 2011, 06:54 AM
  3. Simultaneous Equations
    Posted in the Algebra Forum
    Replies: 2
    Last Post: April 1st 2009, 04:20 AM
  4. Replies: 3
    Last Post: February 27th 2009, 07:05 PM
  5. simultaneous equations
    Posted in the Algebra Forum
    Replies: 1
    Last Post: May 26th 2008, 05:50 AM

Search Tags


/mathhelpforum @mathhelpforum