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Dy/dx

What is dy/dx of 8/root x?

Thanks
Reply 1
Avatar for jamestg
jamestg
21
Original post by Farmerjj
What is dy/dx of 8/root x?

Thanks


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

Thanks


−4 / x^3/2
Reply 3
Avatar for spico
spico
9

Spoiler

Reply 4
Avatar for spico
spico
9
Original post by apronedsamurai
−4 / x^3/2

I am fairly sure that you are missing something there...
Used an online differential calculator :tongue:
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))
Reply 7
Avatar for jamestg
jamestg
21
Original post by apronedsamurai
Used an online differential calculator :tongue:


Trust me, what it came out with is wrong :smile:
Reply 8
Avatar for Farmerjj
Farmerjj
OP
3
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?
Reply 9
Avatar for jamestg
jamestg
21
Original post by Farmerjj
1) 8^-1/2
2) -4
3)-4^-3/2

Is that right?


Perfect! Full marks for you! :thumbsup:
Original post by jamestg
Trust me, what it came out with is wrong :smile:


nope, it just got rid of the minus sign by putting x^-3/2 as 1/x^3/2
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.
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.
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"
Reply 14
Avatar for B_9710
B_9710
18
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.
Reply 15
Avatar for Farmerjj
Farmerjj
OP
3
Original post by jamestg
Perfect! Full marks for you! :thumbsup:


Cheers man 🤓
−4xx\displaystyle \frac{-4}{x\sqrt{x}}
Just another way of putting the same thing.
(edited 8 years ago)
Reply 17
Avatar for B_9710
B_9710
18
Original post by EricPiphany
−4xx\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.
Reply 18
Avatar for spico
spico
9
You're right guys, I didn't see the /
My bad

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