Algebra

Solving Linear Equations and Inequalities

Solve by eliminating x (this is solving 3 linear equations) then substitute to the other two equation

x + y + 5z =2 (1)
4x - 3y + 5z =3 (2)
3x - 2y + 5z=1 (3)

my teacher gave me the answer she said the solution set for this should be {(7,5-2)}

pleeeeeeeeeeeeeaaaseee :(

asked by Clyde
  1. http://www.jiskha.com/display.cgi?id=1461567386#1461567386.1461580442

    posted by Damon
  2. Why eliminate x when the obvious choice would be to eliminate z ??

    #2 - #1 ---> 3x - 4y = 1 **
    #2 - #3 ---> x - y = 2 or x = y+2
    sub that into **
    3(y+2) - 4y = 1
    3y + 6 - 4y = 1
    -y = -5
    y = 5 , then
    x = 7
    back into #1:
    7 + 5 + 5z = 2
    5z = -10
    z = -2

    so the solution is (7,5,-2)

    Depending on the coefficients in the equations, it is often easier to use a combination of methods, rather than one rigid approach

    posted by Reiny
  3. xis what needs to be eliminated. . . my teacher already try eliminated the z

    posted by Clyde
  4. Ok,

    multiply the first by 4, then subtract the 2nd

    multiply the first by 3, then subtract the third.

    Now you have two equations with y's and z's

    carry on

    posted by Reiny

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