Someone who knows some math please help me!

[DeathsHand]

Originally posted by gekko
Here's how I do it.

Step 1: Buy a TI-89 calculator
Step 2: Enter: solve(x-5y=2 and 2x+y=4,{x,y})
Step 3: Write down what it tells you: x=2 and y=0

Now that sounds like my kinda mathish stuff!

Or writing down "I dunno, you tell me."

....

[Jason1]

Hey, Xantar, could you please solve the same problem for me using the substitution method. You dont have to be quite as descriptive, but make sure I still know what your talking about. Thank you.

[Xantar]

Well, I just turned in my psychology paper, so I have nothing better to do.

*hears voices telling him to finish his fanfic*

I was going to do that next!

Anyway, here are your equations again.

x - 5y = 2
2x + y = 4

Substitution means you take one of the equations and get one of the variables all by itself on one side. Hopefully, you know how to move terms from one side of the equation to the other. Just think about it this way: when given a true equation (i.e. 1 + 1 = 2), you can add the same thing to both sides of the equation and it would still be true (1 + 1 + 2 = 2 + 2). You can also multiply both sides by the same number, and it would be true. So in any case, let's say you pick the first equation. If you add 5y to both sides, you'll get

x = 2 + 5y

This is also a true equation. Now that we know this, you can write "2 + 5y" every time you see "x" in the other equation. So the second equation will look like this

2(2 + 5y) + y = 4

Using multiplication (you do know how to multiply in parentheses, don't you?), you can get

4 + 10y + y = 4

which leads to

4 + 11y = 4

If you subtract 4 from both sides, you get

11y = 0

Obviously, then, y = 0. Going back to the first equation, you can plug in 0 every time you see "y" and figure out what x is. In this case,

x - 5(0) = 2

which means x = 2.

You can also start out by solving for y. You can solve for y in the first equation, but that gets ugly. Besides, it's not necessary because in the second equation, you can just move the x term to the other side of the equals sign and you'll have a very neat y = 4 - 2x. You can go from there, plugging in "4 - 2x" into the first equation wherever you see "y" and solve it from there in pretty much the same way as I did before. No matter how you start it out, if you do your math correctly, you will always get the same answer for x and y.

[Jason1]

Thanks Xanny, your the man.

[designated_GM3R]

I thought Substitution was a fairly easy lesson.
Graphing on the other hand sucks balls.

[BreakABone]

*Realizes no one helped him with his math problem*

Thank you all..*CRIES*

[Revival]

Originally posted by BreakABone
*Realizes no one helped him with his math problem*

Thank you all..*CRIES*

*points and laughs*
What math problem?

[Xantar]

Originally posted by BreakABone

A tangent line drawn to the parabola y=4-x2 at the pont (1,3) forms a right triangle with the coordinate axes. The area of the triangle is....

Edit: stupid signs switching on me...ok, here's my second try.

If you take the derivative of the parabola's function, you get dy/dx = -2x. You know that the line intersects at the point (1,3). In other words, where x = 1. Plugging that into the derivative function of the parabola, you get dy/dx = -2.

So now you know the slope of the line is -2 and it passes through the point (1,3). You know how to come up with the equation fo the line from here (I presume). If you want to do this on your own from here, don't read any further. Just check back here to verify your answer.

Are you gone yet? Ok, here goes.

The equation you should get is y = -2x + 5. So you know that the x-intercept is 5/2 and the y-intercept is 5. If you draw everything out on graph paper, you'll see that the base and height of the triangle are 1/2 unit long and 1 unit long respectively. So using the area of a triangle formula, you find that the area of the triangle is 5/2 x 5 x 1/2 or 25/4.

[BreakABone]

Originally posted by Xantar


If you take the derivative of the parabola's function, you get dy/dx = 2x. You know that the line intersects at the point (1,3). In other words, where x = 1. Plugging that into the derivative function of the parabola, you get dy/dx = 2.

So now you know the slope of the line is 2 and it passes through the point (1,3). You know how to come up with the equation fo the line from here (I presume). If you want to do this on your own from here, don't read any further. Just check back here to verify your answer.

Are you gone yet? Ok, here goes.

The equation you should get is y = 2x + 1. So you know that the x-intercept is -1/2 and the y-intercept is 1. If you draw everything out on graph paper, you'll see that the base and height of the triangle are 1/2 unit long and 1 unit long respectively. So using the area of a triangle formula, you find that the area of the triangle is 1/2 x 1/2 x 1 or 1/4.

Well the derivative is wrong..which would throw off your whole problem if done right

But the question is done incorrectly.. I myself can't do it.. but I know the answers and the steps.. just hoping someone could help explain it to me

[Revival]

*explodes*

Stupid math..

[fingersman]

Originally posted by BreakABone


Well the derivative is wrong..which would throw off your whole problem if done right

But the question is done incorrectly.. I myself can't do it.. but I know the answers and the steps.. just hoping someone could help explain it to me

The derivative is right as far as I can tell. x squared gives you 2x. Oh well maybe I read it wrong or something.

BTW how old are you Breakabone?

[Revival]

Mr. Earl Rufus is currently 16, and will be turning 17 on April 2.

[El Gaucho Goof]

Well the derivate of x squared (Don't know how to do it on a Mac) is 2x.. but you also ned to take into account the minus sign in front of it.. Also the problem Xanny did is different from the one I have quoted

Originally posted by Shooter
Mr. Earl Rufus is currently 16, and will be turning 17 on April 2.

As for shooter, he really scares me sometimes, but that is all correct.

[Neo]

sdfsdf*test*

[Revival]

Originally posted by El Gaucho Goof
As for shooter, he really scares me sometimes, but that is all correct.

Heh.. your birthdate is in your profile, and since I hate math, I suck at it, I then went to April on the calendar to see how old you were going to be on April 2nd, and it said 17, so you had to 16 now.

Simple eh?