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DeepRoots
post Sep 19 2007, 04:21 AM
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Anyone out there enjoy a good number crunch? I'm doing A-level maths and am staring blankly at a piece of paper holding a set of questions i just can't do.

just to see how many of you like / can do maths i'll throw one out and see how it goes....

(maybe your proof will help me understand)

Show that the equation of the tangent to the curve
y=7x^2 - 2e^x at the point where x=2 is
y=(28 - 2e^2)x + 2e^2 - 28.

Cheers for your help....if you can handle it ( evil laugh fading out......)
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Ayen
post Sep 19 2007, 04:44 AM
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The answer is 42.

Hope you get the reference tongue.gif

I'd honestly love to help but that looks like someone fell on a keyboard a few times sad.gif.


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blindwillie
post Sep 19 2007, 04:45 AM
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QUOTE (DeepRoots @ Sep 19 2007, 05:21 AM) *
Anyone out there enjoy a good number crunch? I'm doing A-level maths and am staring blankly at a piece of paper holding a set of questions i just can't do.

just to see how many of you like / can do maths i'll throw one out and see how it goes....

(maybe your proof will help me understand)

Show that the equation of the tangent to the curve
y=7x^2 - 2e^x at the point where x=2 is
y=(28 - 2e^2)x + 2e^2 - 28.

Cheers for your help....if you can handle it ( evil laugh fading out......)

I dnt get the bends really. Can you tab it for me? tongue.gif


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DeepRoots
post Sep 19 2007, 04:50 AM
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i guess you guys see this and think the same as i do- "screw this i'm grabbing my guitar".

At this point in the course thats a bad thing for me to be thinking.....

@ Ayen : yeh i get the reference- and that thing hitting the keyboard was my head tongue.gif

@ blindwillie : this type of bend is often a problem for guitarists that arent nerds- just ask your nearest maths teacher for details on this issue cool.gif
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blindwillie
post Sep 19 2007, 04:53 AM
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QUOTE (DeepRoots @ Sep 19 2007, 05:50 AM) *
i guess you guys see this and think the same as i do- "screw this i'm grabbing my guitar".

At this point in the course thats a bad thing for me to be thinking.....

@ Ayen : yeh i get the reference- and that thing hitting the keyboard was my head tongue.gif

@ blindwillie : this type of bend is often a problem for guitarists that arent nerds- just ask your nearest maths teacher for details on this issue cool.gif

Sorry for making a joke of it, just couldn't resist. I'm to no help. I've been through this but I found it boooring and tideous and that stuff didn't stick.


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DeepRoots
post Sep 19 2007, 04:54 AM
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QUOTE (blindwillie @ Sep 19 2007, 04:53 AM) *
Sorry for making a joke of it, just couldn't resist. I'm to no help. I've been through this but I found it boooring and tideous and that stuff didn't stick.


amen to that... dry.gif

cheers anyway smile.gif
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Fsgdjv
post Sep 19 2007, 05:19 AM
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Don't you just derivate (if it's called that in english, I just made that up) it and put x = 2? And then it's done?

I'm sorry if I'm no help, because since you're doing A-level maths (I suppose on university level), the solution must be harder than that, but it looked so easy.. I don't know. Hope I helped, otherwise just ignore me:p


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Resurrection
post Sep 19 2007, 05:22 AM
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QUOTE (DeepRoots @ Sep 19 2007, 04:21 AM) *
Anyone out there enjoy a good number crunch? I'm doing A-level maths and am staring blankly at a piece of paper holding a set of questions i just can't do.

just to see how many of you like / can do maths i'll throw one out and see how it goes....

(maybe your proof will help me understand)

Show that the equation of the tangent to the curve
y=7x^2 - 2e^x at the point where x=2 is
y=(28 - 2e^2)x + 2e^2 - 28.

Cheers for your help....if you can handle it ( evil laugh fading out......)



I'll take a shot. First differentiate y with respect to x using your first equation. This results in dy/dx = 14x - 2e^x and represents the gradient (tangent) at any point. Since we're interested in x=2, plug this value into dy/dx to get a gradient of m = 28 - 2e^2. Since the equation of a straight line is y = mx + c, and we've just found m, we only now need to find the Y-axis intercept c. But we know we've got a straight line passing through the point x=2, y=28 - 2e^2 (from your first equation) AND it has a gradient of 28 - 2e^2. Therefore the line crosses the Y axis at -(28 - 2e^2) or equivalently 2e^2 - 28 and gives us the value of c. So, the equation of the tangent at x=2 is therefore y = (28 - e^2)x + 2e^2 - 28 which agrees with the second equation in your post.

Best of luck in your exam!


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mattacuk
post Sep 19 2007, 07:03 PM
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QUOTE (Resurrection @ Sep 19 2007, 05:22 AM) *
I'll take a shot. First differentiate y with respect to x using your first equation. This results in dy/dx = 14x - 2e^x and represents the gradient (tangent) at any point. Since we're interested in x=2, plug this value into dy/dx to get a gradient of m = 28 - 2e^2. Since the equation of a straight line is y = mx + c, and we've just found m, we only now need to find the Y-axis intercept c. But we know we've got a straight line passing through the point x=2, y=28 - 2e^2 (from your first equation) AND it has a gradient of 28 - 2e^2. Therefore the line crosses the Y axis at -(28 - 2e^2) or equivalently 2e^2 - 28 and gives us the value of c. So, the equation of the tangent at x=2 is therefore y = (28 - e^2)x + 2e^2 - 28 which agrees with the second equation in your post.

Best of luck in your exam!


Well Im impressed blink.gif


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DeepRoots
post Sep 19 2007, 08:30 PM
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QUOTE (Resurrection @ Sep 19 2007, 05:22 AM) *
I'll take a shot. First differentiate y with respect to x using your first equation. This results in dy/dx = 14x - 2e^x and represents the gradient (tangent) at any point. Since we're interested in x=2, plug this value into dy/dx to get a gradient of m = 28 - 2e^2. Since the equation of a straight line is y = mx + c, and we've just found m, we only now need to find the Y-axis intercept c. But we know we've got a straight line passing through the point x=2, y=28 - 2e^2 (from your first equation) AND it has a gradient of 28 - 2e^2. Therefore the line crosses the Y axis at -(28 - 2e^2) or equivalently 2e^2 - 28 and gives us the value of c. So, the equation of the tangent at x=2 is therefore y = (28 - e^2)x + 2e^2 - 28 which agrees with the second equation in your post.

Best of luck in your exam!


wow. that was an awesome explanation. thanks alot ressurrection! much better than my teacher laugh.gif

i hope you dont mind me pestering you via PM for when i get stuck next time.

Great help

This post has been edited by DeepRoots: Sep 19 2007, 08:32 PM
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Andrew Cockburn
post Sep 19 2007, 11:48 PM
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QUOTE (DeepRoots @ Sep 19 2007, 03:30 PM) *
i hope you dont mind me pestering you via PM for when i get stuck next time.


No good deed ever goes unpunished ...


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DeepRoots
post Sep 19 2007, 11:54 PM
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QUOTE (Andrew Cockburn @ Sep 19 2007, 11:48 PM) *
No good deed ever goes unpunished ...


haha! laugh.gif
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botoxfox
post Sep 20 2007, 01:04 AM
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.

This post has been edited by botoxfox: Feb 21 2011, 03:59 PM


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Pavel
post Sep 20 2007, 01:25 AM
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Maths? You gotta be kidding!

I would be of better use in sweeps than in maths biggrin.gif biggrin.gif biggrin.gif


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Iluha
post Sep 20 2007, 02:06 AM
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If you asked me this 2 years ago I would have had an answear for you, but I forgot all my math now.


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FretDancer69
post Sep 20 2007, 06:56 AM
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QUOTE (botoxfox @ Sep 19 2007, 06:04 PM) *
This thread made me remember how much I hate math. wacko.gif dry.gif



yeah i hate it too!!!!! mad.gif mad.gif


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Resurrection
post Sep 23 2007, 07:02 PM
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QUOTE (DeepRoots @ Sep 19 2007, 08:30 PM) *
wow. that was an awesome explanation. thanks alot ressurrection! much better than my teacher laugh.gif

i hope you dont mind me pestering you via PM for when i get stuck next time.

Great help



Glad to have been of help.

To all the other posters, how can you possibly hate mathematics? wink.gif

Seriously though, most of it is getting to grips with terminology, technique and the proper frame of mind. Kinda like guitar playing smile.gif


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botoxfox
post Sep 23 2007, 07:46 PM
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I just find mathematics boring, I wish I didn't, but I just do. I kinda feel that numbers hate me. They just jump up from the paper like shrapnel into my face.


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mattacuk
post Sep 23 2007, 08:36 PM
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Im probably as poor in mathematics as you can get laugh.gif Not because I don’t feel i have the intelligence, rather I wasn’t given the opportunity in school to learn as my class size was huge and teachers rarely turned up sad.gif


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Saoirse O'Shea
post Sep 23 2007, 08:53 PM
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Rightly or wrongly if you want to study any science or science related subject post 16 then a good grounding in maths and/or stats is pretty much a prerequisite.

In the UK in the past you also needed a pass at what was then "O" level grade C (or CSE grade 1) in both English and Maths in addition to the required grades for subjects studies at 'A' level to enter University. My wife had to take her "o" level maths several times to get the pass mark so that she could go to uni despite v good grades in her 'a' levels rolleyes.gif . Have to say that even now it's me that helps our daughter with her maths homework lol: .

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