I really need some help with this math!

Dreamer128 · 01-22-2002, 02:07 PM

Ok, this is my problem. I need to calculate where two lines cross in a graphic, I have the formula of each line. For instance:
H= 0.8*P and H=0.3*P+5.

So we have a method named switching, note how I switch some numbers:
0.8*p= 0.3*P+5
becomes
0.8P*0.3P=5
0.8P*0.3P=0.5 while 5 remains 5.

5:0.5=10

So now we fill it in in the original formulas:
0.8*10=8
0.3*10+5=8

So the crossing point lies at 10,8.

But for some reason this doesnt work with other simulair questions like: 2x-10=4x-24 or 3+0.25p=p+9.

can anyone help me out?

Dreamer128 · 01-22-2002, 02:31 PM

Anyone?

Gray Mage · 01-22-2002, 02:48 PM

quote:
Originally posted by Dreamer128:
Ok, this is my problem. I need to calculate where two lines cross in a graphic, I have the formula of each line. For instance:
H= 0.8*P and H=0.3*P+5.

So we have a method named switching, note how I switch some numbers:
0.8*p= 0.3*P+5
becomes
0.8P*0.3P=5
0.8P*0.3P=0.5 while 5 remains 5.

5:0.5=10

So now we fill it in in the original formulas:
0.8*10=8
0.3*10+5=8

So the crossing point lies at 10,8.

But for some reason this doesnt work with other simulair questions like: 2x-10=4x-24 or 3+0.25p=p+9.

can anyone help me out?

I can't help, but These guys might be able to. They are one of the companies, my company is affiliated with. Hope this helps!!

Vaskez · 01-22-2002, 02:55 PM

Your method looks pretty wrong to me, and I don't know why you use H and P instead of the standard x and y.

if you have y = 0.8x
and y = 0.3x + 5

then simply set the two equations equal to each other as you have done:

0.8x = 0.3x +5

subtract 0.3x from both sides gives you: 0.5x = 5
then divide both sides by 0.5 to give you x = 10

then substitute x = 10 into say the first equation: so y = 0.

10) =8
sp y is 8 and x is 10. Check your answer by substituting into the 2nd equation: 8 = 0.3(10) + 5 = 8 it works so you know 100% sure that you are correct. So the lines cross at the point (10,8) as you said....this method works for ANY pair of simultaneos equations with 2 unknowns. If you have 3 unknowns you need 3 equations etc.

[ 01-22-2002: Message edited by: Vaskez ]

Dreamer128 · 01-22-2002, 03:46 PM

Thanks alot mates, you really helped me out.

01-22-2002, 04:03 PM

Vaskez used the method I would have too.

Simultaneous equations, old boy

Barry the Sprout · 01-22-2002, 04:14 PM

It takes me back! I was doing those with 6 variables before the summer. I am so glad I am not continuing maths at that standard as it would have killed me.

But yeah, Vaskez has it right. Just substitute and it all falls into place. It should all make sense quite easily if you actually think of what the equations mean mathmatically.

Durwyn · 01-22-2002, 04:30 PM

Hmmm? *Scratches head*

Vaskez · 01-22-2002, 05:20 PM

quote:
Originally posted by Barry the Sprout:
It takes me back! I was doing those with 6 variables before the summer. I am so glad I am not continuing maths at that standard as it would have killed me.

But yeah, Vaskez has it right. Just substitute and it all falls into place. It should all make sense quite easily if you actually think of what the equations mean mathmatically.

Hehe, I hope Dreamer never has to do some of the things I'm doing now....Laplace transforms, Sturm-Liouville Systems, Fourier Series, Bode plots and Nyquist Diagrams, Root Locus plots aghhh!

Scholarcs · 01-23-2002, 02:55 AM

quote:
Originally posted by Vaskez:
Hehe, I hope Dreamer never has to do some of the things I'm doing now....Laplace transforms, Sturm-Liouville Systems, Fourier Series, Bode plots and Nyquist Diagrams, Root Locus plots aghhh!

What are you doing at the moment Vaskez? I want to do maths when I leave school (soon) and we do certainly not do that at school. [img]smile.gif[/img]

01-22-2002, 02:48 PM	#3
Gray Mage Banned User Join Date: March 1, 2001 Location: New Jersey Posts: 999	quote: Originally posted by Dreamer128: Ok, this is my problem. I need to calculate where two lines cross in a graphic, I have the formula of each line. For instance: H= 0.8P and H=0.3P+5. So we have a method named switching, note how I switch some numbers: 0.8p= 0.3P+5 becomes 0.8P0.3P=5 0.8P0.3P=0.5 while 5 remains 5. 5:0.5=10 So now we fill it in in the original formulas: 0.810=8 0.310+5=8 So the crossing point lies at 10,8. But for some reason this doesnt work with other simulair questions like: 2x-10=4x-24 or 3+0.25p=p+9. can anyone help me out? I can't help, but These guys might be able to. They are one of the companies, my company is affiliated with. Hope this helps!!

01-22-2002, 02:55 PM	#4
Vaskez Takhisis Follower Join Date: April 30, 2001 Location: szép Magyarország (well not right now) Posts: 5,089	Your method looks pretty wrong to me, and I don't know why you use H and P instead of the standard x and y. if you have y = 0.8x and y = 0.3x + 5 then simply set the two equations equal to each other as you have done: 0.8x = 0.3x +5 subtract 0.3x from both sides gives you: 0.5x = 5 then divide both sides by 0.5 to give you x = 10 then substitute x = 10 into say the first equation: so y = 0.10) =8 sp y is 8 and x is 10. Check your answer by substituting into the 2nd equation: 8 = 0.3(10) + 5 = 8 it works so you know 100% sure that you are correct. So the lines cross at the point (10,8) as you said....this method works for ANY pair of simultaneos equations with 2 unknowns. If you have 3 unknowns you need 3 equations etc. [ 01-22-2002: Message edited by: Vaskez ] __________________ Too set in his ways to ever relate If he could set that aside, there'd be heaven to pay But weathered and aged, time swept him to grave Love conquers all? Damn, I'd say that area's gray

01-22-2002, 04:14 PM	#7
Barry the Sprout White Dragon Join Date: October 19, 2001 Location: York, UK. Age: 41 Posts: 1,815	It takes me back! I was doing those with 6 variables before the summer. I am so glad I am not continuing maths at that standard as it would have killed me. But yeah, Vaskez has it right. Just substitute and it all falls into place. It should all make sense quite easily if you actually think of what the equations mean mathmatically. __________________ [img]\"http://img1.ranchoweb.com/images/sproutman/certwist.gif\" alt=\" - \" /><br /><br /><i>\"And the angels all pallid and wan,<br />Uprising, unveiling, affirm,<br />That the play is the tragedy, man,<br />And its hero the Conquerer Worm.\"</i><br /> - Edgar Allan Poe

01-22-2002, 04:30 PM	#8
Durwyn Elminster Join Date: January 4, 2002 Location: New York Posts: 415	Hmmm? Scratches head __________________ <b>-Durwyn Foehammer</b><p><i>\"Don\'t you go a-meddling with old stone or cold wights or prying in their houses, unless you be strong folk with hearts that never faulter.\"</i> - J.R.R. Tolkien

01-22-2002, 05:20 PM	#9
Vaskez Takhisis Follower Join Date: April 30, 2001 Location: szép Magyarország (well not right now) Posts: 5,089	quote: Originally posted by Barry the Sprout: It takes me back! I was doing those with 6 variables before the summer. I am so glad I am not continuing maths at that standard as it would have killed me. But yeah, Vaskez has it right. Just substitute and it all falls into place. It should all make sense quite easily if you actually think of what the equations mean mathmatically. Hehe, I hope Dreamer never has to do some of the things I'm doing now....Laplace transforms, Sturm-Liouville Systems, Fourier Series, Bode plots and Nyquist Diagrams, Root Locus plots aghhh! __________________ Too set in his ways to ever relate If he could set that aside, there'd be heaven to pay But weathered and aged, time swept him to grave Love conquers all? Damn, I'd say that area's gray

01-22-2002, 02:07 PM	#1
Dreamer128 Dracolisk Join Date: March 21, 2001 Location: Europe Age: 39 Posts: 6,136	Ok, this is my problem. I need to calculate where two lines cross in a graphic, I have the formula of each line. For instance: H= 0.8P and H=0.3P+5. So we have a method named switching, note how I switch some numbers: 0.8p= 0.3P+5 becomes 0.8P0.3P=5 0.8P0.3P=0.5 while 5 remains 5. 5:0.5=10 So now we fill it in in the original formulas: 0.810=8 0.310+5=8 So the crossing point lies at 10,8. But for some reason this doesnt work with other simulair questions like: 2x-10=4x-24 or 3+0.25p=p+9. can anyone help me out?

01-22-2002, 02:31 PM	#2
Dreamer128 Dracolisk Join Date: March 21, 2001 Location: Europe Age: 39 Posts: 6,136	Anyone?

01-22-2002, 03:46 PM	#5
Dreamer128 Dracolisk Join Date: March 21, 2001 Location: Europe Age: 39 Posts: 6,136	Thanks alot mates, you really helped me out.

01-22-2002, 04:03 PM	#6
Lord Shield Guest Posts: n/a	Vaskez used the method I would have too. Simultaneous equations, old boy

01-23-2002, 02:55 AM	#10
Scholarcs Red Dragon Join Date: December 5, 2001 Location: Auckland, New Zealand Age: 38 Posts: 1,557	quote: Originally posted by Vaskez: Hehe, I hope Dreamer never has to do some of the things I'm doing now....Laplace transforms, Sturm-Liouville Systems, Fourier Series, Bode plots and Nyquist Diagrams, Root Locus plots aghhh! What are you doing at the moment Vaskez? I want to do maths when I leave school (soon) and we do certainly not do that at school. [img]smile.gif[/img]

Currently Active Users Viewing This Thread: 1 (0 members and 1 guests)

Similar Threads
Thread	Thread Starter	Forum	Replies	Last Post
need some help from the math savvy	sageridder	General Discussion	5	07-29-2006 02:14 PM
Math Trick	Arvon	General Conversation Archives (11/2000 - 01/2005)	6	08-03-2003 05:14 PM
math?	Gabrielles blades	Neverwinter Nights 1 & 2 Also SoU & HotU Forum	3	02-16-2003 02:17 PM
Math Problem	Ronn_Bman	General Conversation Archives (11/2000 - 01/2005)	7	11-13-2002 04:19 AM
The Math?	hitherebobby	Baldurs Gate II: Shadows of Amn & Throne of Bhaal	2	03-07-2002 02:31 PM