How do you solve 5x + y = 8 and –4x – 4y = – 16 using substitution?

1 Answer
Apr 18, 2018

x=1 and y=3

Explanation:

So always when you try to solve systems, if you find either a single y or x then use the substitution, just something I always do. Anyway so here we have

5x+y=8
-4x-4y=-16

And in the first one we have a single y ( shown below)

5x+color(red)(y)=8
-4x-4y=-16

Now we re-write it to get:

color(red)(y) =8-5x
-4x-4y=-16

Put this equation :
color(red)(y) =8-5x

into the other to get:

-4x-4(8-5x)=-16

Simplify:

-4x-32+20x=-16

Simplify more:

16x=16

Divide 16 on both sides to get:

x=1

Now put that into any equation to get:

5+y=8

Simplify to get

y=3

Now check you work by putting in the numbers into the other equation to get:

-4(1)-4(3)=-16
-4-12=-16

So it's right with

x=1
y=3

Hope this helps!