Ogaar
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Evaluate
d/dx x^(n) + 5x

x=1 below d/dx
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mqb2766
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(Original post by Ogaar)
Evaluate
d/dx x^(n) + 5x

x=1 below d/dx
What do you mean by the second part?
Last edited by mqb2766; 1 month ago
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Ogaar
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(Original post by mqb2766)
What do you mean by the second part?
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This is the question
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mqb2766
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(Original post by Ogaar)
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This is the question
Which part are you having trouble with? It looks straightforward.
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Ogaar
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(Original post by mqb2766)
Which part are you having trouble with? It looks straightforward.
Well, haven’t really done any evaluation like this at A-Level.
My answer was n^(n-1) + 5 but apparently this is wrong.
The question after is simple as well but I can’t do it either. It was sin(t) with the text below saying t = pi.
Apparently the answer can’t be cos(pi) as it must be an integer or decimal so I put zero as well but apparently that was wrong too. Maybe I’m just answering them wrong?
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mqb2766
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(Original post by Ogaar)
Well, haven’t really done any evaluation like this at A-Level.
My answer was n^(n-1) + 5 but apparently this is wrong.
The question after is simple as well but I can’t do it either. It was sin(t) with the text below saying t = pi.
Apparently the answer can’t be cos(pi) as it must be an integer or decimal so I put zero as well but apparently that was wrong too. Maybe I’m just answering them wrong?
How do you differentiate x^2, x^3, ..., x^n? Spot the pattern. Then 1^(n-1) =...
You must have covered this.
Last edited by mqb2766; 1 month ago
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DFranklin
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Notation means: "find d/dx for the expression, the final answer is what you get when you substitute x=1 into that expression".
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Ogaar
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(Original post by DFranklin)
Notation means: "find d/dx for the expression, the final answer is what you get when you substitute x=1 into that expression".
Thank you. I’ve never been really taught notation by my college for some reason
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Ogaar
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(Original post by mqb2766)
How do you differentiate x^2, x^3, ..., x^n? Spot the pattern. Then 1^(n-1) =...
You must have covered this.
Yeah I’m pretty rusty after the long break, I was having trouble with the notation mainly as I had never encountered it before
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Ogaar
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#10
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(Original post by DFranklin)
Notation means: "find d/dx for the expression, the final answer is what you get when you substitute x=1 into that expression".
Wait, surely the final answer depends on what n is then? I have n(1)^(n-1) + 5(1) but this isn’t correct...
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mqb2766
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1^(n-1) = ...
So the answer is ...
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Ogaar
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#12
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(Original post by mqb2766)
1^(n-1) = ...
So the answer is ...
Where have you only got 1 from? Surely it’s n^(n-1). If it’s 1 then overall obviously it equals 1 + 5 = 6 but that’s not correct...
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mqb2766
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(Original post by Ogaar)
Where have you only got 1 from? Surely it’s n^(n-1). If it’s 1 then overall obviously it equals 1 + 5 = 6 but that’s not correct...
What is the derivative of x^3?
Where is the x term in your expression n^(n-1)? Is this before or after you sub x=1.
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Ogaar
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(Original post by mqb2766)
What is the derivative of x^3?
Where is the x term in your expression n^(n-1)? Is this before or after you sub x=1
Oh I get you now man. I’m being stupid. Anything multiplied by 1 is 1. So 1^n-1 is 1... but how come the answer isn’t 6 then? I’ve tried that before.
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mqb2766
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(Original post by Ogaar)
Oh I get you now man. I’m being stupid. Anything multiplied by 1 is 1. So 1^n-1 is 1... but how come the answer isn’t 6 then? I’ve tried that before.
You are rusty :-).
What is the derivative before you sub x=1?
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Ogaar
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#16
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(Original post by mqb2766)
You are rusty :-).
What is the derivative before you sub x=1?
nx^(n-1) + 5
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mqb2766
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(Original post by Ogaar)
nx^(n-1) + 5
Ok so sub x=1 and remember there are two operations in the first term: multiplication and power.
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Ogaar
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(Original post by mqb2766)
Ok so sub x=1 and remember there are two operations in the first term: multiplication and power.
You end up with the indice not having an effect first, since 1 to the power of anything is 1. Then you just have nx + 5, which isn’t the correct answer btw
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mqb2766
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(Original post by Ogaar)
You end up with the indice not having an effect first, since 1 to the power of anything is 1. Then you just have nx + 5, which isn’t the correct answer btw
Why x in that expression? You've replaced it with 1?
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Ogaar
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#20
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(Original post by mqb2766)
Why x in that expression? You've replaced it with 1?
I meant n + 5, my bad. Thank you for solving my problem, I feel like an idiot rn. This is what happens when you don’t do maths for 4 months.
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