FAZ
Premium Member
Registered: 24th Nov 07
Location: Coventry
User status: Offline
|
just cant for the life of me remeber how todo this shizz
|
3CorsaMeal
Member
Registered: 11th Apr 02
User status: Offline
|
i can remember
|
pow
Premium Member
Registered: 11th Sep 06
Location: Hazlemere, Buckinghamshire
User status: Offline
|
It's a quadratic, simplifies to x^2 + 3x - 4 = 0
Just got to solve that
[Edited on 18-01-2012 by pow]
|
Ian
Site Administrator
Registered: 28th Aug 99
Location: Liverpool
User status: Offline
|
Multiply both sides by 2x+6 to get
24 = 3x * 2x + 6
Expand that out until you get a proper polynomial so its in the form
0 = ax^2 + bx + c
if you want to find roots use the solver -
http://upload.wikimedia.org/wikipedia/en/math/8/e/4/8e4fef5352eb498b3534af481c8c4fd4.png
|
FAZ
Premium Member
Registered: 24th Nov 07
Location: Coventry
User status: Offline
|
cheers guys
 its obvious now youve put that
thank you
[Edited on 18-01-2012 by FAZ]
|
pow
Premium Member
Registered: 11th Sep 06
Location: Hazlemere, Buckinghamshire
User status: Offline
|
It's been a while but I've got 1.095 and -4.095
|
FAZ
Premium Member
Registered: 24th Nov 07
Location: Coventry
User status: Offline
|
i got 1.09..... and -4.096...
 ta
|
pow
Premium Member
Registered: 11th Sep 06
Location: Hazlemere, Buckinghamshire
User status: Offline
|
FAZ 
|
FAZ
Premium Member
Registered: 24th Nov 07
Location: Coventry
User status: Offline
|
24 = 3x * 2x +6
-6
18 = 3x * 2x
bit of trial and error later, answer is roughly 1.732323....
what we had done pow was come from a simultaneous equation angle, which isnt what it wants, as it needs a single answer for x, my bad, didnt realise til i wa slike wtf, 2 answers 
[Edited on 18-01-2012 by FAZ]
|
3CorsaMeal
Member
Registered: 11th Apr 02
User status: Offline
|
so you got 18 = 6x, then give the answer as 1.7?
|
3CorsaMeal
Member
Registered: 11th Apr 02
User status: Offline
|
i get X=1
just from looking at it
|
Ian
Site Administrator
Registered: 28th Aug 99
Location: Liverpool
User status: Offline
|
Sorry I rushed it, you need to enforce the bodmas when you expand out the first multiplication
|
FAZ
Premium Member
Registered: 24th Nov 07
Location: Coventry
User status: Offline
|
what s hite day im having
|
3CorsaMeal
Member
Registered: 11th Apr 02
User status: Offline
|
just take the X's away, none of these funny terms needed
24/8 = 3
|
Dom
Member
Registered: 13th Sep 03
User status: Offline
|
quote:
Originally posted by 3CorsaMeal
i get X=1
just from looking at it
Yup, looked at it thought one then saw Pow's/Faz's answers and been trying to work out where the .7 is coming from
[Edited on 18-01-2012 by Dom]
|
Steve
Premium Member
Registered: 30th Mar 02
Location: Worcestershire Drives: Defender
User status: Offline
|
|
pow
Premium Member
Registered: 11th Sep 06
Location: Hazlemere, Buckinghamshire
User status: Offline
|
Jim it's a quadratic, in the form ax^2 + bx + c = 0
You can't just 'solve' that, you plug the values into the quadratic equation. As you have a square root in there you end up with two possible answers (IE. the line is a curve on a graph so theres two points of intercestion).
Start by *'ing both sides by 2x + 6 so:
24 = 3x(2x + 6)
Out the brackets:
24 = 6x^2 + 18x
Move the 24 over
6x^2 + 18x - 24 = 0
For neatness divide by 6
x^2 + 3x - 4 = 0
Put it into this:
gives you 1.095 and -4.096 to 2 DP.
Graph looks like:
You can see the answer is right as it crosses the x axis at about 1 and -4.
A thank you goodnight. Just taking the x's away, it asks you to solve x
[Edited on 18-01-2012 by pow]
|
3CorsaMeal
Member
Registered: 11th Apr 02
User status: Offline
|
my answer was right though?
|
pow
Premium Member
Registered: 11th Sep 06
Location: Hazlemere, Buckinghamshire
User status: Offline
|
Well, it wasn't.
|
3CorsaMeal
Member
Registered: 11th Apr 02
User status: Offline
|
24/(-8+6) = -12
is that what your saying?
|
pow
Premium Member
Registered: 11th Sep 06
Location: Hazlemere, Buckinghamshire
User status: Offline
|
It's 5 years ago since I even touched on this but I think I'm right, that equation plots a graph that is U shaped, hence the two intercestion points, hence the two answers. When you square root something you end up with two possible answers (hence +/-).
I'm happy to be proved wrong though!
|
Steve
Premium Member
Registered: 30th Mar 02
Location: Worcestershire Drives: Defender
User status: Offline
|
|
pow
Premium Member
Registered: 11th Sep 06
Location: Hazlemere, Buckinghamshire
User status: Offline
|
Go on then Steve?
|
3CorsaMeal
Member
Registered: 11th Apr 02
User status: Offline
|
being good at math is part of my aspergers
|
Dom
Member
Registered: 13th Sep 03
User status: Offline
|
24 / (2x + 6) = 3x
24 = (3X(2X + 6)
24 = 6x^2 + 18x
4 = x^2 + 3x
x = 1
It asks to 'calculate x', so it's after a single value. However, there is probably more values that work other than 1.
[Edited on 18-01-2012 by Dom]
|
