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Author simple maths
pow
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18th Jan 12 at 12:55   View Garage View User's Profile U2U Member Reply With Quote
Dom, can you explain this step:

4 = x^2 + 3x

x = 1
pow
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18th Jan 12 at 12:57   View Garage View User's Profile U2U Member Reply With Quote
They always do that 'calculate x' thing to trick you into thinking there is one value. Happened all the time in my A LEvel
3CorsaMeal
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18th Jan 12 at 13:00   View User's Profile U2U Member Reply With Quote
have you put -4 back into the original equation yet pow?
Dom
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18th Jan 12 at 13:06   View User's Profile U2U Member Reply With Quote
quote:
Originally posted by pow
They always do that 'calculate x' thing to trick you into thinking there is one value. Happened all the time in my A LEvel


Didn't do A Level maths so can't comment, but never saw variables being represented as two values whilst doing maths for acoustics and filter design during uni.

Either way I stand by my answer of x = 1.
adiohead
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18th Jan 12 at 14:56   View User's Profile U2U Member Reply With Quote
as it says "simple maths", I would put 1 too.
Ian
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18th Jan 12 at 15:37   View Garage View User's Profile U2U Member Reply With Quote
Edit - give me a minute

[Edited on 19-01-2012 by Ian]
Ian
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18th Jan 12 at 15:53   View Garage View User's Profile U2U Member Reply With Quote
quote:
Originally posted by pow
They always do that 'calculate x' thing to trick you into thinking there is one value.
Its not a trick, its just that x has multiple roots because the quadratic is not commutative, ie. you can't reverse the operation using a square root because you'll get the positive root only.

The actual solution if you want just one answer is to minimise the quadratic equation as far as you can but not expand out the +/- bit.
LeeM
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18th Jan 12 at 15:59   View User's Profile U2U Member Reply With Quote
6x^2 - 18 = 0
Then apply quadratic formula, x = 0 or -3

Probably wrong, I'm hungover
3CorsaMeal
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18th Jan 12 at 19:20   View User's Profile U2U Member Reply With Quote
i think we need another one, as this was too simple imo.
FAZ
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19th Jan 12 at 11:52   View Garage View User's Profile U2U Member Reply With Quote
4x / 5x+2 = 3

just for you jim

[Edited on 19-01-2012 by FAZ]
3CorsaMeal
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19th Jan 12 at 11:55   View User's Profile U2U Member Reply With Quote
so something divide by something is equal to 3, thats how i start off.

3CorsaMeal
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19th Jan 12 at 11:56   View User's Profile U2U Member Reply With Quote
did you just make that up btw? as from a quick glance it seems abit unrealistic to me
FAZ
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19th Jan 12 at 11:58   View Garage View User's Profile U2U Member Reply With Quote
taken from the same question paper, uni aerospace 208 control module year 1 was the question previous to my OP one
3CorsaMeal
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19th Jan 12 at 12:29   View User's Profile U2U Member Reply With Quote
preferred the other one, i can only get to

4x/15x = 6

and that seems impossible with real numbers, does it make a bendy line?
Dom
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19th Jan 12 at 12:35   View User's Profile U2U Member Reply With Quote
quote:
Originally posted by 3CorsaMeal
and that seems impossible with real numbers, does it make a bendy line?


FLOL

I await Pow for his answer and graph

If this is Year 1 maths, then it'll be foundation and more GCSE than A-Level.

Edit - Just notice Ian has edited his length answer as well....

[Edited on 19-01-2012 by Dom]
3CorsaMeal
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19th Jan 12 at 12:37   View User's Profile U2U Member Reply With Quote
Got his dad to help him lastnight imo
Paul_J
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19th Jan 12 at 12:49   View User's Profile U2U Member Reply With Quote
quote:
Originally posted by Dom
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.


I agree with this.
Dom
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19th Jan 12 at 12:50   View User's Profile U2U Member Reply With Quote
You're wrong Paul, haven't done a pretty graph.
Paul_J
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19th Jan 12 at 12:52   View User's Profile U2U Member Reply With Quote
Although I just re - read pow's answer and I now see what he's saying
pow
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19th Jan 12 at 13:32   View Garage View User's Profile U2U Member Reply With Quote
The graph was made using an online thing that took me all of 20 seconds?

[Edited on 19-01-2012 by pow]
LeeM
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19th Jan 12 at 13:41   View User's Profile U2U Member Reply With Quote
oh its 6x^2+18x-24=0
x=-4 or 1


[Edited on 19-01-2012 by LeeM]
pow
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19th Jan 12 at 13:43   View Garage View User's Profile U2U Member Reply With Quote
a thank you.
pow
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19th Jan 12 at 13:47   View Garage View User's Profile U2U Member Reply With Quote
quote:
Originally posted by FAZ
4x / 5x+2 = 3

just for you jim

[Edited on 19-01-2012 by FAZ]


x = -0.18

x's all on one side there so it's a peice of piss that one
Nath
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19th Jan 12 at 13:47   View User's Profile U2U Member Reply With Quote
I hated math and this is why.
Dom
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quote:
Originally posted by pow
a thank you.


You said and, which was the issue I had......

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