Question

How would I solve these equations using the substitution method?
y=x-2
y=-x+8

Answer 1

what does it mean to substitute?

Answer 2

it means to replace with an equivalent form ..... if they insist that y=x-2. then every where you see a y, substitute it with the form: x-2, and solve for x

Answer 3

so the equation now becomes x-2=x-2?

Answer 4

the top one does, which granted is of little use to us; but they give us that bottom one which helps out alot when we substitute :)

Answer 5

y = -x+8

x - 2 = -x + 8

now that one we can get a good value for x from

Answer 6

How would I solve this?

Answer 7

would the orderedpair just be (-2,8)?

Answer 8

Using substitution, we can substitute x-2 in place of y in the second equation.
x - 2 = -x + 8. Add 2 to both sides.
x = -x + 8 + 2. Add x to one side.
x + x = 8 + 2.
2x = 10. Divide by 2.
x = 5.
So your first number in the ordered pair would be (5,y).
Use the value found for x to find the value of y.
y = x - 2.
y = (5) - 2.
Solve. :) This will give you the value for y in the ordered pair (x,y)

Answer 9

Thank you sooo much!

Answer 10

since solving for 1 equation in 1 variable is covered extensively before solving 2 equations in 2 variables; i assumed you would have known how to find a solution to:

x-2 = -x+8

Answer 11

Can you guys help me with one more?
The question is x+2y=-3
x=-3y

For x+2y=-3 I substituted in x and got -3y+2y=-3
From there I added a three to each side and got y+2=0
Then I subtracted 2 from each side and got y=-2
Then I substituted y into the equation x=-3y and I got 6
So in the end my ordered pair was (6,-2)
The website is saying I got it wrong though, can you tell me what I did wrong?

Answer 12

You mistake happened when you added three to each side.
\[-3y + 2y \neq y\]

Answer 13

Instead you should have gotten -y + 2 = 0.

Answer 14

I'm confused :/what do I do after I get -3y+2y=-3

Answer 15

Oh, oops. -y + 2 = 0 is not right.

You did good you just added the y's wrong :) And you want to make sure you keep the variable isolated, don't try to add numbers back onto the same side of the equation as the variable.
-3y + 2y = -3.
-1y = -3
y = 3.