Question

What's the best first step to eliminate the y-value in the system of equations?
x + 8y = –4
2x – 4y = –13

Answer 1

System of Equations will be the death of me...

Answer 2

How the hell does this make sense? Has anyone ever been far even as decided to use even go want to do look more like?

Answer 3

hey

Answer 4

hai. :)

Answer 5

you can add equations together
its no different from adding numbers together

Answer 6

some equation = -4
some equation = -13
so if i add -4-13
that is the same as adding those 2 equations together

Answer 7

I know i need to multiply one of the two equations by 2 or -2.

Answer 8

that is the theory behind it

Answer 9

now u just want to add in a way so that one of those variables is eliminated

Answer 10

notice the functions themselves
$$
\begin{matrix}
x& \color{blue}{+ 8y} &= &–4\\
2x & \color{blue}{– 4y} &= &–13
\end{matrix}
$$

to eliminate "y" you'd want to make the "y's" the same value but different sign
so above you have +8y, so
+8y
-8y
-----
0
thus eliminated

Answer 11

-6*

Answer 12

x + 8y = –4
(2x – 4y = –13) *2 -->(4x – 8y = –26)
add them
x + 8y = –4
4x – 8y = –26
--------------
5x = -30
x =-6

Answer 13

i only need the first step, heres the review question im stuck on:

Select the best possible first step to solving the system by first eliminating the y variable.
x + 8y = –4
2x – 4y = –13

a. Multiply the first equation by 2.
b. Multiply the second equation by 2.
c. Multiply the first equation by –2.
d. Multiply the second equation by –2.

Answer 14

Hello, my name is Compassionate. But you already know that, ya? System of equations is fairly easy. There are two methods that are very easy to use. The first method is called the Elimination method and the second method is called the substitution method.

They both have different usages. Foe example, in the substitution method, you SOLVE for either equation then substitute it into the other equation. For example:

x = y + 3
x + y = 2

I can see here that x is already solved. So if I know what x equals then I just plug it into the equation.

(y + 3) + y = 2
y + 2 + y = 2, now, I just solve for y. And once I solve for y -- I plug y into either equation, and there we go! I got my x and y points.

Now the elimination method is different. We want to ELIMINATE a term, either x or y, then solve. In the equations above:
x + 8y = –4
2x – 4y = –13

We can eliminate either one. But lets eliminate x first.
So, what do you need to multiply EITHER of the equations by to get them to cancel x terms? Well, wee need to multiply the first one by NEGATIVE 2.

-2(x + 8y = -4)
2x - 4y = - 13

-2x - 16y = 8
2x - 4y = - 13

Now, we see, upon adding, the xs will cancel.
-20y = -5

Now we just solve like a normal equation (Because we eliminated x, we're just left to solve for y!)

y = -20/-5
y = 4

(Remember, dividing a negative by a negative = positive)

SO, now that you know that y = 4, take 4 and plug it into EITHER of the equations and solve it for X! :) You can do the rest. I believe in you!

Answer 15

none of your answers have matched, or come close to, A.,B.,C., or D.

Answer 16

C.! C is for Compassionate! Thank you! You went out of your way and solved the full damn thing too! Thanks!

Answer 17

You're welcome ~~

Answer 18

All I needed: We can eliminate either one. But lets eliminate x first.
So, what do you need to multiply EITHER of the equations by to get them to cancel x terms? Well, wee need to multiply the first one by NEGATIVE 2.

Answer 19

lol xD no

Answer 20

Thank you everybody for trying.

Answer 21

Hold up there, Davis, I may have made a slight miscalculation

Answer 22

could you try this one @Compassionate?

Eliminate the x-value.
4x + 9y = 21
3x – 8y = 1

a. ultiply the first equation by 3 and multiply the second equation by 4.
b. Multiply the first equation by –3 and multiply the second equation by –4.
c. Multiply the first equation by 8 and multiply the second equation by 9.
d. None of the above

Answer 23

pellet.

Answer 24

No problem, Davis, can you give me a minute to calculate something?

Thanks ~

Answer 25

Hey, sorry for the short wait. Would you mind browsing Facebook, messing around on YouTube? Or is this a timed test. I'm at BK and making an order currently. Can you wait a few minutes?

Answer 26

it's like you know me perfectly, im on Facebook, and YouTube, and its just an entry-review.

Answer 27

Alright. They sort of ran out of ice cream and whatnot. So I'm having to wait on that.

Answer 28

(I'm talking about your original question)

The first equation can be multiplied by 2 or negative two... it just seems easier to multiply it by 2 and solve for y. So, it should be, "Multiply the first one by 2"

This one makes more sense. I admit, I had to look at it for awhile. While it doesn't matter if we multiply it by 2 or -2, doing so by 2 eliminates a single step.

Answer 29

it should be "multiply the 2nd one by 2"

Answer 30

Okay, thank you for clearing that up with me, it's just these types of questions I dont understand.

Answer 31

the SECOND* okay

Answer 32

your original question wants you to eliminate y

Answer 33

So B? and if you understand so well Dan, do the second question.

Answer 34

While Compassionate enjoys some BK Ice Cream.

Answer 35

Oops! Dan is right! I didn't read it correctly. It wants you to eliminate Y first. So multiply the second one by 2. SORRY! Read it wrong. But I hope you now understand how to solve system of equations!

Answer 36

ehh, it needs more than one example for me to understand things. usually two of the same thing.

Answer 37

sure ill give you another example :)

Answer 38

3x + 2y =5
x-6y=3
eliminate y

Answer 39

Eliminate the x-value.
4x + 9y = 21
3x – 8y = 1

a. ultiply the first equation by 3 and multiply the second equation by 4.
b. Multiply the first equation by –3 and multiply the second equation by –4.
c. Multiply the first equation by 8 and multiply the second equation by 9.
d. None of the above

Answer 40

mine has multiple choice, which is what i have to do for my review, and my test.

Answer 41

well do this one,
3x + 2y =5
x-6y=3
eliminate y

Answer 42

what will be your first step?

Answer 43

hello??

Answer 44

help me help you

Answer 45

Listen to Dan, Davis, help us help you.

Answer 46

y=mx+b form?

Answer 47

i'm clueless...

Answer 48

We want to eliminate x:

4x + 9y = 21
3x – 8y = 1

that is: 4x and 3x

What do we need to multiply 4x and 3x by to get them BOTH to cancel?

Answer 49

like i said, clueless..

Answer 50

What is the lowest common multiple of 4 and 3?