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-   -   Maths Help. (http://forums.sv650.org/showthread.php?t=169100)

MisterTommyH 26-07-11 11:44 AM
Maths Help.
 
Anyone out there really good at maths?

It's been ages since I've done anything complicated and I've completely forgotten lots of it.

Anyone know how to solve:

18x^3 + 340x = 6351 :confused:

Reeder 26-07-11 01:22 PM
Re: Maths Help.
 
No :D

Bluefish 26-07-11 01:27 PM
Re: Maths Help.
 
Google hth.

MisterTommyH 26-07-11 01:34 PM
Re: Maths Help.
 
Lol. Didn't think so. Google didn't particularly help.

Syduck 26-07-11 02:37 PM
Re: Maths Help.
 
Try this
http://www.wolframalpha.com/input/?i=18x^3%20%2B%20340x%20%3D%206351&t=crmtb01
HTH

keithd 26-07-11 02:41 PM
Re: Maths Help.
 
Is it George Best?

fenjer 26-07-11 03:03 PM
Re: Maths Help.
 
x is just less than 1.01

HTH

:)

Luckypants 26-07-11 03:19 PM
Re: Maths Help.
 
Quote:
Originally Posted by Syduck (Post 2579214)
:winner:

I had got 6.175 using an approximation (needed Google to jog my memory though) but 6.18053 works out almost exactly. Useful site for O-level maths, if we had the internet back then ;)

MisterTommyH 26-07-11 04:37 PM
Re: Maths Help.
 
Brilliant. Thanks guys. We'd got it to 'just over 6', but needed a bit more of an accurate answer than that.

This is the problem with all the good software these days - it makes you forget all the useful stuff you've learned.

Viney 26-07-11 04:44 PM
Re: Maths Help.
 
Quote:
Originally Posted by Tommy H (Post 2579265)
Brilliant. Thanks guys. We'd got it to 'just over 6', but needed a bit more of an accurate answer than that.

This is the problem with all the good software these days - it makes you forget all the useful stuff you've learned.
You mean there was useful stuff to learn. Bugger!

Ed 26-07-11 08:48 PM
Re: Maths Help.
 
I still have my old slide rule:D

timwilky 26-07-11 10:01 PM
Re: Maths Help.
 
Quote:
Originally Posted by Ed (Post 2579448)
I still have my old slide rule:D
But can you remember how to use your guessing stick.


Multiplication/division
any root

the rest I have forgotten how to use logarithmic scales

Kilted Ginger 26-07-11 10:20 PM
Re: Maths Help.
 
Sure i've a book of logarithims up the loft. remember to show your working.

Venom 26-07-11 10:25 PM
Re: Maths Help.
 
Quote:
Originally Posted by Kilted Ginger (Post 2579561)
Sure i've a book of logarithims up the loft. remember to show your working.
My old maths teacher used to joke that logs were introduced by a constipated mathematician. He used to crack terrible jokes all the time

mikerj 26-07-11 11:21 PM
Re: Maths Help.
 
18x^3+340x-6351=0 is a cubic equation so has three roots. However, two of them are complex roots:

6.180531691302737
-3.0902658456513685+6.89478918309233i
-3.0902658456513685-6.89478918309233i

Use the Cubic solver here

Professor 27-07-11 08:46 AM
Re: Maths Help.
 
Quote:
Originally Posted by mikerj (Post 2579585)
18x^3+340x-6351=0 is a cubic equation so has three roots. However, two of them are complex roots:

6.180531691302737
-3.0902658456513685+6.89478918309233i
-3.0902658456513685-6.89478918309233i

Use the Cubic solver here
Respek!

Winder 27-07-11 12:14 PM
Re: Maths Help.
 
What is ^3 mean?

Is it 18x cubed?

timwilky 27-07-11 12:18 PM
Re: Maths Help.
 
Shorthand used to signify cubed etc. x³ is difficult to type unless you know all the alt characters and hope the reader has the correct character set.

MisterTommyH 27-07-11 02:53 PM
Re: Maths Help.
 
Plus when you find an online calculator like those posted above (Or mathcad if you can afford the license) it often won't recognise x³ so asks you to input it as x^3


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