EpicTree
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Not sure if this is the right part of the forum to post for help but, I've tried for absolutely ages how to work these out, I really don't know how to solve them and they're due in for tomorrow so any help would be greatly appreciated
here's the sheet
and this is my attempt of what I could do on the first one. you see I differentiated it and now I don't know what to do. I suck at math so could anyone explain step by step how you can do any of the questions?
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TenOfThem
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(Original post by EpicTree)
and this is my attempt of what I could do on the first one. you see I differentiated it and now I don't know what to do. I suck at math so could anyone explain step by step how you can do any of the questions?
You have differentiated 5x^3 + 6x^2

But then you have not differentiated 3x + 8 - why not
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EpicTree
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(Original post by TenOfThem)
You have differentiated 5x^3 + 6x^2

But then you have not differentiated 3x + 8 - why not
How do you do that? would it be 3x^0 and how would you differentiate 8?
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TenOfThem
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(Original post by EpicTree)
How do you do that? would it be 3x^0 and how would you differentiate 8?
No

Well 3x differentiates to 3x^0, yes and of course x^0=1

8 is already 8x^0


Have you missed some lessons - this is step one and you seem to be much further on than step one given some of the questions
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EpicTree
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(Original post by TenOfThem)
No

Well 3x differentiates to 3x^0, yes and of course x^0=1

8 is already 8x^0


Have you missed some lessons - this is step one and you seem to be much further on than step one given some of the questions
No, been in all my lessons but I didn't fully understand it to be honest
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TenOfThem
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(Original post by EpicTree)
No, been in all my lessons but I didn't fully understand it to be honest
If you are struggling with something this simple you really need to sit down with your teacher to go through the basics of differentiation
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Elm Tree
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(Original post by EpicTree)
How do you do that? would it be 3x^0 and how would you differentiate 8?
When you differentiate a number with just an x next to it, you just get rid of the x.
So differentiating 3x would turn out to be 3

And when you differentiate a number by itself, it always gives you zero.
Differentiating 8 would be 0

The final answer should be 152-12x+3

http://www.examsolutions.net/ - Good videos on how to do maths problems here.
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suirrel
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How much do you know about powers? Did you miss any lessons at the very very beginning of the year about powers and indices?

To differentiate an equation, you should use this: [ y = (ax)^n ] is differentiated into [ dy/dx = (anx)^n-1 ]

In practice, this means that: [ y = 3x^4 ] is differentiated into [ dy/dx = 12x^3 ]

Because you multiply the 3 and the 4 together to make 12x, and then take 1 from 4 in the power.

When a number has "no" powers written on it, such as [ 2x ], this means that it really is [ 2x^1 ], however it is convention to not write the ^1. In practice this means that [ 2x ] in this case would become [ 2x^0 ], or just [ 2 ]. Also, a number without an "x" turns into zero, i.e. you do not write it, as it disappears.

Example:

[ y = 5x^2 + 4x + 8 ] is differentiated into [ dy/dx = 10x + 4 ]

[y = 14x^0.5 + 2x^3 + 5 ] , [ dy/dx = 7x^-0.5 + 6x^2 ]

[y = 2^(9/8) + 3^(1/3) + 2 ] , [dy/dx = (18/8)x^(1/8) + x^(-2/3) ]


Does this help at all??
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