substitute method for x + y - z =4

Question

i have to use the substitute method for this problem:

  x+y-z=4

3x+2y+4z=17

-x+5y+z=8

i dont know how to do this

Answer 1

In the first equation we can solve for x buy subtracting y and adding z to both sides:

 

x=-y +z +4

 

Now substitute this "value" of x into the second and third equations. 

 

This will give you two new equations with only two unknowns then you can solve those as "simultaneous equations" with 2 variables.

 

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