solve by elimination

Question

X=-5

x-3y+4x=1

2x+5y-z=-3  (-5,2,3)

Answer 1

I believe you have a typo in your questions, but I figure out where is the typo as well.  

 

x - 3y + 4z = 1    Not 4x.  If it is 4x, your teacher should put 5x - 3y = 1  and that make the answer a little bit ugly

 

Ok, substitute -5 to x in all the equations, so you only have two equations with two different variables.

 

-5 - 3y + 4z = 1

-10 + 5y - z = -3

 

The easiest way is to make the second equation "z" term to be -4z.  So we multiply the 4 on both side of the second equations:  -40 + 20y -4z = -12

 

-5 - 3y + 4z = 1

-40 + 20y -4z = -12

 

To combine them, you add the two equations together

 

-45 + 17y = -11

17y = 34

y = 2

 

Substitute x and y back into any of the original equations

 

-5 -  3(2) + 4z = 1

-11 + 4z = 1

4z = 12

z = 3

 

(-5, 2, 3)

 

To verify your answer, substitute x, y, z to the other original equation

 

2(-5) + 5(2) - 3 = -3

-10 + 10 - 3 = -3

-3 = -3

 

All checked