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Find the gradient of the function at x=4

Here is the question: Find the gradient of the function at x=4

y=(3x^3 -2)/(x(x^1/2))

The answer is 291/32 but I keep getting weird answers like 9/2(2^1/2) + 3(1/32^1/2)

Could someone explain how you get to the answer of 291/32



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I have a solution coming give me 2 minutes :-)
Original post by Fanta4TheBanter
I have a solution coming give me 2 minutes :-)


Full solutions are NOT allowed.

@OP:

Show the working you have done so far, most likely there is some mistake in your application on the quotient rule.
Original post by Fanta4TheBanter
I have a solution coming give me 2 minutes :-)


Please do not post a full solution as that is against the forum guidelines
Original post by Mysticmeg
Here is the question: Find the gradient of the function at x=4

y=(3x^3 -2)/(x(x^1/2))

The answer is 291/32 but I keep getting weird answers like 9/2(2^1/2) + 3(1/32^1/2)

Could someone explain how you get to the answer of 291/32





Is your question y=3x3−2x32y = \dfrac{3x^3-2}{x^{\frac{3}{2}}} ?
Original post by TenOfThem
Please do not post a full solution as that is against the forum guidelines


Sorry, I didn't know about this.
Original post by Fanta4TheBanter
Sorry, I didn't know about this.


NP

:smile:

There is a sticky on the front page of maths
Not going to lie I don't see what's wrong with posting a solution. They can see where their working has gone wrong by looking against the correct solution.
Original post by Fanta4TheBanter
Not going to lie I don't see what's wrong with posting a solution. They can see where their working has gone wrong by looking against the correct solution.


http://www.thestudentroom.co.uk/showthread.php?t=403989

If the OP had posted a solution we could have helped with mis-conceptions
Original post by TenOfThem
http://www.thestudentroom.co.uk/showthread.php?t=403989

If the OP had posted a solution we could have helped with mis-conceptions


Checked it. Once again, sorry.
Original post by Mysticmeg
Here is the question: Find the gradient of the function at x=4

y=(3x^3 -2)/(x(x^1/2))

The answer is 291/32 but I keep getting weird answers like 9/2(2^1/2) + 3(1/32^1/2)

Could someone explain how you get to the answer of 291/32





Ok. Let us see the working you have so far...
Original post by Fanta4TheBanter
Checked it. Once again, sorry.


Not a problem :smile:

We all did the same at first
Reply 12
Avatar for Mysticmeg
Mysticmeg
OP
10
Original post by TenOfThem
Is your question y=3x3−2x32y = \dfrac{3x^3-2}{x^{\frac{3}{2}}} ?


No i tried using latex but failed miserably It's that apart from on the bottom of the fraction its x times square root of x.

I would post working but it's pretty incoherent and I have no idea what I'm doing.

For dy/dx I got 9/2(x^(1/2)) + 3(x^(-5/2))
(edited 9 years ago)
Original post by Mysticmeg
No i tried using latex but failed miserably It's that apart from on the bottom of the fraction its x times square root of x.


That is the same

I would post working but it's pretty incoherent and I have no why what I'm doing.

For dy/dx I got 9/2(x^(1/2)) + 3(x^(-5/2))


I agree

Now 412=24^{\frac{1}{2}} = 2 so there should be no roots in your answer
(edited 9 years ago)
Reply 14
Avatar for Jagerm7
Jagerm7
Original post by Mysticmeg
Here is the question: Find the gradient of the function at x=4

y=(3x^3 -2)/(x(x^1/2))

The answer is 291/32 but I keep getting weird answers like 9/2(2^1/2) + 3(1/32^1/2)

Could someone explain how you get to the answer of 291/32





Use the quotient rule, you can rewrite x(x^1/2) as x^3/2 unless the uv'+vu' is needed there not sure
Reply 15
Avatar for Mysticmeg
Mysticmeg
OP
10
Original post by alex2100x
Full solutions are NOT allowed.

@OP:

Show the working you have done so far, most likely there is some mistake in your application on the quotient rule.



I don't even know what the quotient rule is...
Original post by Jagerm7
Use the quotient rule, you can rewrite x(x^1/2) as x^3/2 unless the uv'+vu' is needed there not sure


There is no need to use the quotient rule

This is much simpler than that - the OP has correctly differentiated
Original post by Mysticmeg
I don't even know what the quotient rule is...


Do not worry - they are being silly

I think you have used x=2 instead of x=4
Reply 18
Avatar for Mysticmeg
Mysticmeg
OP
10
Original post by TenOfThem
Do not worry - they are being silly

I think you have used x=2 instead of x=4


I'm not sure what I did but I have the answer now. thanks :redface:
Original post by TenOfThem
Do not worry - they are being silly

I think you have used x=2 instead of x=4


No you definitely need the quotient rule, unless you want to bring the x3/2 x^{3/2} up to the top line by multiplying, but that just makes it awkward.

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