Question

Part 1: Explain, in complete sentences, how you would use the substitution method to solve the following system of equations. (3 points)

Part 2: Provide the solution to the system. (1 point)

5x – y = –1
7x – 3y = 13

Answer 1

I can explain how I would use substitution, but keep in mind there are other ways.
First I would use the first equation to isolate y.

Answer 2

u dont need to use substitution to solve this problem!

Answer 3

I want to try and use substitution.

Answer 4

I know elimination isbetter

Answer 5

this is accomplished as follows. Add y to both sides of the equal sign of the first equation getting: y-1=5x. I would then add 1 to both sides of this equation getting: y=5x+1. this has now isolated y and its value is substituted for the y in the second equation. Follow so far?

Answer 6

yes, but i just learned this so im a little rough, can you continue

Answer 7

you have to isolate the y right?

Answer 8

Yes now substituting for the y in the second equation. Remember that we have already determined that y=5x+1. When substituted for y in the second equation we would now have: 7x-3y=13 or 7x-3(5x+1)=13 Do you see where y was placed in the term -3y ?

Answer 9

Please review my second post to determine how we isolated y.

Answer 10

Uhhh i think so. but i dont kow how to finish it all off. Do i just cancel everything?

Answer 11

By substituting the isolated value for y in the second equation, we now have one equation in one unknown. That is 7x-15x-3=13. All you have to do is to read and understand these posts.

Answer 12

Ohh oh i c now.

Answer 13

Do you know how to solve 7x-15x-3=13 ?? Using the common principles of algebra.

Answer 14

yuppp. that helps

Answer 15

Just remember the Golden Rule, " what ones does to one side of the equal sign, one must do the same thing to the other side"

Answer 16

I think you have it but I will continue. Combine the x terms getting: -8x-3=13
Now add 3 to both sides getting -8x=16
Divide both sides by -8 getting x=-2
You now have x. Substitute this in one of the original equations (your choice of which one) and then solve for y.

Answer 17

Ok, thanks bro!

Answer 18

yes! thats what i got for x and now y is simple.

Answer 19

did you get y=4?

Answer 20

You're welcome and you are now on your way. good luck with these system of linear equations.

Answer 21

yeah?

Answer 22

Let me check 5x-y=-1
5(-2)-y=-1
-10-y=-1 Doesn't look like I am going to get the same thing as you did.

Answer 23

Double check you work, pay real close attention to your signs!

Answer 24

hmmmm. ill recheck my math. thanks for the help!

Answer 25

Which equation did you choose to substitute the -2 for x?

Answer 26

7x-3y=13

Answer 27

So substituting -2 for x that would look like: 7(-2) - 3y = 13
-14 -3y = 13 adding +14 to both sides gets us
-3y = 27 dividing by both sides by -3 get us
y = 9 Where did you stray off the "straight and narrow"?

Answer 28

That should be a -9 please excuse the typo?

Answer 29

See how easy it is to get signs confused!

Answer 30

Earth to @NashNugs are you breathing?

Answer 31

I have tried to comply with your problem, the sentences were supposed to be complete.

Answer 32

Ooops sorry! I was just trying to figure out the proble. I got -9 i see where i goofed up!

Answer 33

take care. Where did you goof up? Just curious.

Answer 34

Thanks! Oh i substituted wrong.

Answer 35

i gotta go! i appreciate it sir!