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?
3 answers
I am super confused.
Darn I really hope Reiny comes on.
the name substitution tells you how to solve the system.
From the first equation, you know that
z = 8-x-y
Now, substitute that into the other two equations. That gives you
-4x+4y+5(8-x-y)=7
2x+2(8-x-y)=4
or,
-9x-y = -33
-2y = -12
Now you can see that
y=6
Thus, -9x-6=-33, so x = 3
And finally, z=8-3-6 = -1
From the first equation, you know that
z = 8-x-y
Now, substitute that into the other two equations. That gives you
-4x+4y+5(8-x-y)=7
2x+2(8-x-y)=4
or,
-9x-y = -33
-2y = -12
Now you can see that
y=6
Thus, -9x-6=-33, so x = 3
And finally, z=8-3-6 = -1