Asked by Olivia N J

Solve the system by substitution.

-x-y-z=-8
-4x+4y+5z=7
2x+2z=4

I am very confused about this. Can someone please explain how to do this?

Answers

Answered by Reiny
The actual steps will vary from person to person, and there is no single way to solve this.
You sort of have to decide on the simplest equation as a starting point.
In this case it is the last equation, it only has two variables.
2x + 2z = 4 , or
x + z = 2 ---> x = 2-z
I will now sub that into the 1st and the 2nd

-x-y-z=-8 ----> x + y + z = 8
2-z + y + z = 8
y = 6 ----> well that was lucky

in the 2nd:
-4x + 4y + 5z = 7
-4(2-z) + 24 + 5z = 7
-8 + 4z + 24 + 5z = 7
9z = -9
z = -1
then x = 2-z = 2+1 = 3

x = 3
y = 6
z = -1
Answered by Olivia N J
THANK YOU!!!!!!!!!!
Answered by Reiny
you are welcome
Answered by DDM
8 x 4 = 32 not 24 XD
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