Dy/dx Watch

Farmerjj
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#1
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What is dy/dx of 8/root x?

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jamestg
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(Original post by Farmerjj)
What is dy/dx of 8/root x?

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1) get rid of the fraction and get it in the form axn
2) multiply the coefficient by the power
3) minus one from the power
4) there's your answer
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User947387
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(Original post by Farmerjj)
What is dy/dx of 8/root x?

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−4 / x^3/2
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spico
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If you follow the above rules you will see that you need to find f '(x) when f(x)= 8x^ (-1/2) (8x to the power of minus a half) so 8 multiplied by minus a half is -4, minus 1 from the power for -3/2, so dy/dx = -4x^-3/2 (minus 4x to the power of minus 3 over 2(1.5)
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spico
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(Original post by apronedsamurai)
−4 / x^3/2
I am fairly sure that you are missing something there...
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User947387
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Used an online differential calculator
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Mathematicus65
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Firstly change 8/(rt(x)) to 8/(x^(1/2)). Then move the variable from the denominator into the numerator by giving the power the opposite sign. Ie. change ^(1/2) to ^(-1/2) so you now have 8x^-(1/2). Then differentiate as normal to obtain -4x^(-3/2) which is them rewritten as -4/(x^(3/2))
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jamestg
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(Original post by apronedsamurai)
Used an online differential calculator
Trust me, what it came out with is wrong
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Farmerjj
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(Original post by jamestg)
1) get rid of the fraction and get it in the form axn
2) multiply the coefficient by the power
3) minus one from the power
4) there's your answer
1) 8^-1/2
2) -4
3)-4^-3/2

Is that right?
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jamestg
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(Original post by Farmerjj)
1) 8^-1/2
2) -4
3)-4^-3/2

Is that right?
Perfect! Full marks for you! :thumbsup:
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09sstinson
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(Original post by jamestg)
Trust me, what it came out with is wrong
nope, it just got rid of the minus sign by putting x^-3/2 as 1/x^3/2
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jamestg
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(Original post by 09sstinson)
nope, it just got rid of the minus sign by putting x^-3/2 as 1/x^3/2
Exam boards prefer you to have your answer in the form axn unless it says otherwise in the question.
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User947387
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No harm done eh guys? Was the correct answer given by each of us...we just expressed it in a different but mathematically valid way.
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09sstinson
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(Original post by jamestg)
Exam boards prefer you to have your answer in the form axn unless it says otherwise in the question.
that may be true but putting the answer in a different form is not "wrong"
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B_9710
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(Original post by jamestg)
Exam boards prefer you to have your answer in the form axn unless it says otherwise in the question.
It doesn't matter what form you give any of your answers in as long as it is correct and it doesn't ask for a specific form in the question. A correct answer is a correct answer so how could it be marked wrong.
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Farmerjj
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(Original post by jamestg)
Perfect! Full marks for you! :thumbsup:
Cheers man 🤓
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EricPiphany
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\displaystyle \frac{-4}{x\sqrt{x}}
Just another way of putting the same thing.
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B_9710
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#18
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(Original post by EricPiphany)
\displaystyle \frac{-4}{x\sqrt{x}}
Just another way of putting the same thing.
That is the form that is probably the easiest to compute dy/dx for values of x on a calculator. It is the easier form to read and understand as you don't have the negative fraction exponents.
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spico
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#19
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You're right guys, I didn't see the /
My bad
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