Math

posted by .

Solve the system using any algebraic method.
2x - 2y + z = 3
5y - z = -31
x + 3y + 2z = -21
______________________
The answer I got for this is ( -26, 6,67) but I know its wrong and I don't know why. Help please >< my work is at the bottom

I used substitution method changed 5y-z=-31 to z=5y+31 then I:
Plugged it in the first equation=
2x-2y+5y+31=3 -> 2x+3y+31=3 -> 2x+3y=-28 is my new 1st equation...
Plugged in z=5y+31 to equation 3 =
x+3y+2(5y+31)=-21 -> x+3y+10y+62=-21 -> x+13y+62=-21 -> x+13y=-83 is my new 2nd equation.
2(=13y=82)+3y=-28 -> -26-166+3y=-28 -> -23y=138 - > y=6
2x+3(6)=-28 -> 2x+18=-28 -> 2x=-46 -> x=-23
2(-26)-2*6)+z=3 -> -52-12+z=3 -> -64+z=3 -> z=67

  • Math -

    5y - z = -31

    z = 5y + 31



    2x - 2y + z = 3

    ( Now put z = 5y + 31 in equation )

    2x - 2y + 5y + 31 = 3

    2x + 3y = 3 - 31

    2x + 3y = - 28

    2x = - 28 - 3y Divide both sides with 2

    x = - 14 - ( 3 / 2 ) y



    x + 3y + 2z = -21

    ( Now put x = - 14 - ( 3 / 2 ) y and z = 5y + 31 in equation )

    - 14 - ( 3 / 2 ) y + 3y + 2 ( 5y + 31 ) = - 21

    - 14 - ( 3 / 2 ) y + 3y + 10y + 62 = - 21

    - ( 3 / 2 ) y + 13y = - 21 + 14 - 62

    - ( 3 / 2 ) y + ( 26 / 2 ) y = - 69

    ( 23 / 2 ) y = - 69 Multiply both sides with 2

    23y = - 138 Divide both sides with 23

    y = - 6



    z = 5y + 31

    z = 5 ( -6 ) + 31

    z = - 30 + 31

    z = 1



    x = - 14 - ( 3 / 2 ) y

    x = - 14 - ( 3 / 2 ) -6

    x = - 14 + 18 / 2

    x = - 14 + 9

    x = - 5


    So solutions are :

    x = - 5

    y = - 6

    z = 1

Respond to this Question

First Name
School Subject
Your Answer

Similar Questions

  1. Algebra

    Checking a few answers to some algebra problems: 1.Find the slope of the line that passes through the points (-4,1) and (3,5). I got m = 5-1 / 3-(4) Answer is m = 4/7 2.Find the equation, in slope-intercept form, of the line that passes …
  2. Math(Solve the system)

    So I guess I have to: Solve the system using any algebraic method. I'm not sure how so here is the problem I'm stuck on. 9x-5y=-30 x+2y=-3
  3. Algebra 2

    Solve the system using any algebraic method. 22.)2x-5y=4 23.)5x+7y=12 24.)3x-4y=6 3x+4y=9 3x-2y=8 4x+7y=1 Thanks!
  4. MaTh = Algebra = help

    Solve this system of linear equaiton by an algebraic method. So If I had to solve this the elimination method way, how would I do it?
  5. algebra 1

    Solve the following system of linear equation using any algebraic method. 2x+5y=3 X-3y=7
  6. algebra 1

    Solve the following system of linear equation using any algebraic method. 2x+5y=3 X-3y=7
  7. algebra 1

    Solve the following system of linear equation using any algebraic method. 2x+5y=3 X-3y=7
  8. MATH

    Find the solution/point of intersection of the following quadratic-linear system. Show steps appropriately: y+x^2=-6x-3 and x+y-1=0. Solve using both an algebraic and graphical method.
  9. Algebra-Multiple choice

    Hello, I have some practice math I'm working through and I'm unsure about the answer. I will also put what I got. Thanks for the help. 1. Solve using any method and identify the system as consistent, inconsistent, or dependent. -2x+y=8 …
  10. Algebra Multiple Choice

    Hello, This is the last of questions I have for my practice assignment. Again I will put what I got. Thanks for your help. 1.) Solve the system using substitution. Write answer as an ordered pair. 4x+2y=8 -5x-2=y A.) First equation …

More Similar Questions