Friday

August 1, 2014

August 1, 2014

Posted by **Paula** on Monday, March 22, 2010 at 3:56am.

3x+4y+z=7

2y+z=3

-5x+3y+8z=-31

- math -
**Reiny**, Monday, March 22, 2010 at 8:37amthe middle equation is nice and gives us

z = 3-2y

sub that into the first and third

1) 3x + 4y + 3 - 2y = 7

3x + 2y = 4 (#1)

3) -5x + 3y + 8(3-2y) = -31

-5x + 3y + 24 - 16y = -31

-5x - 13y = -55

5x + 13y = 55 (#3)

#1 by 5: 15x + 10y = 20

#3 by 3: 15x + 39y = 165

subtract them ...

29y = 145

y = 5

back in #1

3x + 2y = 4

3x + 10 = 4

x = -2

back into the middle

2y + z = 3

10 + z = 3

z = -7

x = -2, y = 5, z = -7

**Related Questions**

Math 116 - Consider the following system of equations. y=2x-2 y-2x=9 What can ...

Math 1 - Consider the following system of equations. y = 4x - 4 y - 4x = 3 What...

math 20 system of equations - I have been solving system of equations ...

math - Consider the following system of equations. Y = 3x – 7 Y - 3x = 5 a) The ...

Math - Sustem of equations. I have to solve the system of equations by graphing ...

Business Algebra - Produce an example of a system of equations to your fellow ...

Algebra - When solving a system of equations by the addition method, how do you ...

Algebra - When solving a system of equations by the addition method, how do you ...

Algebra 2 - 1. What is the first step for solving this system by substitution? ...

Math - Solving systems of equations with three variables? What is the solution ...