Question

Need help
Solve the system by substitution
-x-y-z=-8
-4x+4y+5z=7
2x+2z=4
show all your work

Answer 1

first isolate x in the third equation so
2x + 2z = 4 => 2x = -2z + 4 => x= -z + 2
then you can plug x into the first equation and reduce so
-x -y -z = -8 => -(-z+2)-y-z=-8 => z-2-y-z=-8 => y=6
substitute x and y into the second equation so
-4x+4y+5z=7 => -4(-z+2)+4(6)+5z=7 => 4z-8+24+5z=7
=> 9z=-9 => z=-1
then you can substitute z into the third equation to find x
2x+2z=4 => 2x+2(-1)=4 => 2x-2=4 => 2x=6 => x=3

so x=3, y=6, and z=-1

Answer 2

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