Math Help

[Rev7]

Yeah, I don't want to be spamming the Math is Cool thread so I thought that I should make this.

 

Well, ya I need some help with my math homework. ASAP would be helpful...<snip> I just need help

Solve by using elimination:

8x+3y+5=0

10 x+6y+13

 

and:

x/4-y/3=1

1/3x-4y/9=4/3

 

I would greatly appretiate any help...

[Rabish Bini]

I'd love to help but I don't think I understand the question correctly...

[Inyri]

If you "mainly just forgot" then just check that section in your text book.

[Rev7]

Okay.

 

Example:

 

2x+y=1

3x-y=14

 

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Work:

 

5x=15

 

x=3

 

2(3)+y=1

6+y=1

-6 -6

 

y=-5

Final Answer:

 

(3,-5)

 

This is on my homework, and I have no one to help me. I have attemped them, but am a little stuck and need some help. That is all.

[Rabish Bini]

10 x+6y+13

I think you left out the answer for this one

[Rev7]

^

sorry...

 

8x+3y+5=0

10 x+6y+13

 

Show spoiler

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(-3) 8x+3y+5=0

 

=

 

-24x-6y-15=-3

 

___

 

-24x-3y-15=-3

+

10 x+6y+13=0

_____________________

-14x-2=-3

 

-14x=-1

This is where I am stuck.

 

If you "mainly just forgot" then just check that section in your text book.

It is on a worksheet.

 

EDIT:

I see my mistake in that...fixed...still stuck though

[Inyri]

I understand it's a worksheet. Pull out your book and read that section.

 

If you didn't bring your book home with you to do your homework, take this as your lesson learned.

[Rev7]

My teacher gaves us notes, and explained how to do it and I understand how to do it...it is just that I am stuck on these problems.

[HerbieZ]

Math only taught me one thing. If the guy is using letters instead of numbers to work out the bill, punch him in the face.

[Rabish Bini]

Math only taught me one thing. If the guy is using letters instead of numbers to work out the bill, punch him in the face.

They're know as Pro-numerals, punching him in the face seems like the logical thing to do

 

I'm trying to figure out the answers Rev7, but I'm a bit stuck as to the answer in the second line of the first question, I do believe there's supposed to be an answer there, or am I missing something?

[Rev7]

10x+6y+13=0

 

I forgot the zero, I think. My bad...

[Arcesious]

And you said you would have the skills to help me if I needed help, lol.

 

Your math looks slightly more advanced than what I'm at at the moment. My Algebra class is doing those same kinds of equations, and tommorw is when I bet we'll be using fractions...

 

Although I think I understand this already...

 

My advice: Eliminate the smallest variable term first.

 

Example:

 

7n-2=5n + 6

-5n -5n

2n - 2 = 6

+ 2 + 2

2n = 8

/2 /2

n = 4

 

 

In this, the variable is n. one side had 7n, one side has 5n. You get rid of the lesser variable first. I got rid of 5n first. As for negative variables and positive variables - get rid of the negative variable first. (or the negative variable farthest from 0) Think of integers. Anything less than 0 is smaller than anything more than 0...

 

IE:

 

for -5n and -7n, -7n is the smaller variable term.

[Inyri]

That works fine if there's only one variable. His work has two different variables.

[Arcesious]

That works fine if there's only one variable. His work has two different variables.

 

Oh... I can't brain today, I have the dumb. lol.

 

Forget what I said Rev7... I guess I actually have no idea how to do what you're doing there...

[Rev7]

What we are doing is solving systems of equations Algebraically.

 

Eventually we will make graphs with them. This is a review for me, it is just it has been a good year before I last did something like this and I got stuck. Today's homework is/was on the hard side.

 

@Arc--what you were doing is correct, my equations are just a little bit more....advanced/harder/have more steps...I understand what you are doing.

[Boba Rhett]

Solve for 3y and then substitute in the second line:

 

8x + 3y + 5 = 0

 

10x + 6y + 13 = 0

 

=> first line = 3y = -8x - 5 So Second line equals,

 

10x + 2(-8x - 5) + 13 = 0

 

10x + -16x - 10 + 13 = 0

 

-6x + 3 = 0

 

-6x = -3

 

6x = 3

 

x = .5

 

 

Test:

 

4 + 3y + 5 = 0

 

3y = -9

 

y = -3

 

Test:

 

10(.5) + 6(-3) + 13 = 0

 

5 + -18 + 13 = 0

 

=> True

[Da_man]

Dammit Rhett beat me to it. It's Systems of Equations' right?

[tk102]

(-3) 8x+3y+5=0

 

=

 

-24x-6y-15=-3

False...

 

8x + 3y + 5 = 0

x -3

------------

-24x -9y -15 = 0

 

 

 

Hint:

Try -2 instead of -3... then add the two equations to eliminate the y variables.

[Boba Rhett]

Good lord, I dunno. Do you have any idea how much Sudafed is in me right now? I just do maths.

[Litofsky]

If I remember this type of equation correctly, as tk mentioned, you 'line up' the equations, eliminate one of the two variables, and go to town.

 

Example:

 

5x+2y=5

x+3y=-7.5

 

Now, since none of the variables are equal, we need to make 'em equal. So, let's try to get the "x" variables equal.

 

5x+2y=5

(NOTE: in order to get the "x"s equal, we need to multiply this equation by -5. -5, so that the two will cancel out [-5+5=0]Therefore...) x(-5)+3(-5)y=-7.5(-5)

 

Now simplified:

5x+2y=5

-5x-15y=37.5

 

"X"s cancel out...

 

2y=5

-15y=37.5

 

Now, if I did that correctly, "y" should equal 2.5 Go back into the equation, plug "y" in, and you should be able to solve the one-variable equation.

 

I hope that helps.

[Inyri]

I prefer solving for Y and making the equations equal, but I don't think that's 'solving by elimination.'

[Litofsky]

I prefer solving for Y and making the equations equal, but I don't think that's 'solving by elimination.'

 

Maybe it isn't. It's been a while since I've done this, so I might have remembered incorrectly.

[Inyri]

I dunno, this is the bit I always hated about math. Having to do something a 'certain way' when it's obviously not the best way.

[Nedak]

Oh you're solving for X.

 

I'd do it but I don't remember stuff from 8th grade (that's when I learned it).

[Boba Rhett]

You dun remember teh algebras?