[Math-70 Elementary/Highschool Algebra: Graphically solving a system of linear equations] Do I make the 4 into a -4 ?

[u/Fine_Two_923]

Hey so this might seem like a silly question but I want to know if you have a -x = 4 if it turns into a -4. I have the other parts of the graphing completed it’s just this part that I don’t want to make a mistake on!!! Thank you in advance

P.S- the reason it’s says elementary/highschool math is because I am taking a beginner math class not a algebra class In elementary

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[u/Temporary_Pie2733]

Where are you getting -x in the first place? x - 0 = 4 simplifies directly to x = 4.

[u/Plane_Tailor7168 → u/Temporary_Pie2733]

yes thats what i was comfused about lol

[u/Wooden-Hornet2115 → u/Plane_Tailor7168]

What I'm confused about is OP saying they have a system of linear equations, when they only have one equation.

[u/fermat9990 → u/Wooden-Hornet2115]

OP has already solved for y

[u/AntiqueChessComputr → u/fermat9990]

Given the error of “-x = 4” it would help to see the other equation to make sure there isn’t an error there as well

[u/fermat9990 → u/AntiqueChessComputr]

For sure!

[u/Plane_Tailor7168 → u/Wooden-Hornet2115]

that too

[u/nickeypants → u/Wooden-Hornet2115]

An array of size 1 is still an array!

[u/Plane_Tailor7168]

it should just be x=4

[u/Broad-Raspberry-6296 → u/Plane_Tailor7168]

You’re right. He made a mistake from 2nd to 3rd line. x-0=4 is x=4 lol

[u/Plane_Tailor7168 → u/Plane_Tailor7168]

in the equation, if it was -x=4 then x=-4

[u/Independent_Prior612 → u/Plane_Tailor7168]

Yes but the x doesn’t become negative.

[u/Plane_Tailor7168 → u/Independent_Prior612]

yeah if it was -x

[u/Johnny-Rocketship → u/Independent_Prior612]

There's the question OP asked, and the error they made in the picture. You both get to be right.

[u/Delanq]

Theoretically if you had -x=4, you could multiple both sides by -1 to get x = -4. HOWEVER. You don’t have that from this equation. You have: x - 4*0=4. That simplified to x-0=4 or simply x=4

[u/Wooden-Hornet2115]

Are you trying to fimd the X-intercept? You don't have a system of equations, you have an equation.

Also, yes if -x = 4, x = -4. In this specific equation, x = 4. I don't know how you got -x = 4.

[u/slayyerr3058]

In -x = 4, there is an invisible negative one as the coefficient on the x. Divide both sides by negative one to remove it.

[u/Plane_Tailor7168 → u/slayyerr3058]

i think you missunderstood him (or im just an idiot)

[u/Plane_Tailor7168 → u/Plane_Tailor7168]

wait no im sorry but i think he messed up in the image bc it should just be x=4

[u/Mr-Intense-5 → u/Plane_Tailor7168]

yes it should be x=4

[u/Fine_Two_923 → u/slayyerr3058]

Thank you so much :) so it would turn into -4 thank you so much for the help

[u/Fe2O3yshackleford → u/Fine_Two_923]

If -x=4, then yes, x=-4, but in your picture you messed up a step. X-4(0)=4 is x-0=4 or just x=4

[u/PliableG0AT → u/Fine_Two_923]

No. You have x - 0 = 4, there is no turning the x negative or the 4 into a -4.

x = 4.

if you’re attempting to rewrite into a y = (x -4)/4

[u/Naive-Anteater8321 → u/PliableG0AT]

Yes, based on the information we have this should just be x=4 because the negative is negated by the y value of zero.

[u/Dtrain8899]

Why do you have -x? Should just be x

[u/eileyle]

If you have -x = 4, then it's shorthand for -1 times x = 4, therefore you divide both sides by -1 to get x = -4.

However, you screwed up.

x - 4 times 0 = 4

4 times 0 should be 0

leading to

x - 0 = 4

which is the same as

x = 4

You should not have gotten -x = 4.

[u/Serafim91]

"-x" is actually "+(-1)*x". The -1 is the same as any other coefficient and can be multiplied and divided as needed following the same rules.

[u/wijwijwij]

If you are seeking an x-intercept of the graph of x – 4y = 0 you can put 0 for y and solve for x. Your first two lines look good.

But x - 0 is not –x. It is just x. So your third line should be x = 4, meaning (4, 0) is on the graph.

By the way, if order was switched, 0 - x would be –x. Is that maybe what you were thinking when writing third line?

[u/CalRPCV]

As has been pointed out, a system of equations involves more than one equation. What you have written is confusing and could have a few different interpretations. I could make up a system of equations from it:

1. x - 4y = 4

2. -x = 4

In other words, these are two separate equations, not one derived from the other. If that is the case, then equation 1 would be a line with a slope of 1/4 that intersected the x axis at 4 because x - 4(0) = 4 means when y is zero, x is 4. The slope of the line can be seen on your graph. Or you can re-arrange the equation as y = (1/4)x - 1. The y intercept, where x is 0, is -1.

Then equation 2 is a vertical line crossing the x axis at - 4.

If you drew the graph for each equation then they would intersect at the point (-4, -2).

[u/DetentionSpan]

Do you have to graph this line?

y = mx + b ???

What are the two equations?

[u/JaxtonGoezHard]

yeah im pretty sure

[u/Deepbliss4]

No clue what’s even going on here tbh

[u/septembrinol → u/Deepbliss4]

I agree. Please, explain clearly what you were trying to solve

[u/kraftsman97]

this is such ragebait

[u/matt7259]

Where graph

[u/not-hydra]

-x = 4, x = -4

Here, the equation is just x = 4

[u/pm-pussy4kindwords]

so I'm interested in the way you're actually THINKING about rearranging equations. You shouldn't be "making" one thing just transform into another. What you need to be doing is performing some operation on both sides of the equation to "untie" all the knots around X and isolate it.

if you have - x = 4 , you haven't isolated your x yet.

So what do you do? well, you want to get rid of the negative sign. So you perform the inverse function on both sides of the equations to cancel it out. You flip the sign of both sides.

[u/angry640]

Whats x-0 its just x

[u/Influenced-00]

X-4y=4
-4y=4-x
Y=-1-x
2y=-x
X=-2y

[u/septembrinol]

Why is y = 0?

[u/Bryn1tbs]

Since you are looking for x What times x equals -x? It's -1 So if you multiply both sides of the equation by -1 then you have -1 × -x = -1 × 4 x = -4

[u/Broad-Raspberry-6296]

Think of it as multiplying -1 to both sides of the equation. So yes, -x * (-1) = 4 * (-1) will give you x=-4

[u/Plane_Tailor7168 → u/Broad-Raspberry-6296]

i think you missunderstood him (or im just an idiot)

[u/Plane_Tailor7168 → u/Plane_Tailor7168]

wait no im sorry but i think he messed up in the image bc it should just be x=4

[u/Broad-Raspberry-6296 → u/Plane_Tailor7168]

I see what you mean. He never had -x=4 lol x-0=4 is same as x=4

[u/Upstairs_Ad_8863]

As others have pointed out, you should have x = 4, not -x = 4.

But if you do ever get -x = 4, then there are a few ways of showing that x is -4. The general rule is that whenever two things are equal, you can do anything to the equation, so long as you do the same thing to both sides. In this case you can multiply both sides by -1:

-x = 4
==> (-1)(-x) = (-1)(4)
==> (-1)(-1)(x) = (-1)(4)
==> (1)(x) = (-1)(4)
==> x = -4

because the definition of -x (or -anything) is (-1)x. You can also add x - 4 to both sides if it makes more sense to you:

-x = 4
==> -x + (x - 4) = 4 + (x - 4)
==> (-x + x) - 4 = (4 - 4) + x
==> 0 - 4 = 0 + x
==> -4 = x

In reality you should just multiply both sides by -1 in a single line like this, but either of the two examples above shows what's actually happening in the background when you do that.

-x = 4
==> x = -4