Question

Consider the following pair of equations:

y = x + 4
y = −2x − 2

Explain how you will solve the pair of equations by substitution. Show all the steps and write the solution in (x, y) form.

Answer 1

by doing substitution, you are effectively combining the two equations together. Therefore, we need to change the easier equation so that it would be equal to x

Answer 2

The key thing here is that if we set an equation equal to x, then we can plug in that equation in place of the x in the second equation.

Answer 3

Following me so far? @Taya1431

Answer 4

So right now, I want you to set y=x+4 so that it equals x

So solve for x.

Answer 5

x=y-4

Answer 6

yes. So now that we know x is equal to y-4, we can insert this into the other equation.
We are "substituting" the variable for an actual definition.

y=-2(y-4)-2

^
Now we only have one variable, so we can solve for y

Answer 7

Do you see what I did there?

Answer 8

so you subtract the 2?

Answer 9

you replace the "x" in the second equation with "y-4"

and before you subtract the two, distribute the -2 into the parentheses. Can you do that for me?

Answer 10

uh.. like this? ~ 2=2-4

Answer 11

No, you still have the two...Here, let me show you what I mean by distribution.
And sorry for the late replies, my internet is being really weird

Answer 12

its cool x3

Answer 13

oh..

Answer 14

So we went from this:
y=-2(y-4)