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A-Level Maths: Pure Math 1 marker

The curve with equation y=x^(5/2) .lnx/4 where x>0 crosses the x-axis at the point P. Write the coordinates of P.

The answer is (4,0)

I can't seem to figure out the coordinates of this x intersect. It's only a 1 marker so it is quite frustrating...

All help is greatly appreciated
Reply 1
Avatar for mqb2766
mqb2766
21
Original post by That_Guy_Omzz
The curve with equation y=x^(5/2) .lnx/4 where x>0 crosses the x-axis at the point P. Write the coordinates of P.

The answer is (4,0)

I can't seem to figure out the coordinates of this x intersect. It's only a 1 marker so it is quite frustrating...

All help is greatly appreciated


Can you upload a picture of the question pls
Edit ahh misread the missing brackets in ln(x/4)?
(edited 4 years ago)
Original post by That_Guy_Omzz
The curve with equation y=x^(5/2) .lnx/4 where x>0 crosses the x-axis at the point P. Write the coordinates of P.

The answer is (4,0)

I can't seem to figure out the coordinates of this x intersect. It's only a 1 marker so it is quite frustrating...

All help is greatly appreciated

Why do you think that x=0 is not accepted as a valid solution? (Hint - recall your log knowledge).
In which case, what must make y=0?

Edit: Now that we have the original question, we can ignore my first sentence.
(edited 4 years ago)
Original post by mqb2766
Can you upload a picture of the question pls
Edit ahh misread the missing brackets in ln(x/4)?

Here
Hard 1 marker.PNG36.0KB
Reply 4
Avatar for mqb2766
mqb2766
21
Original post by That_Guy_Omzz
Here

So you have the product of two functions. One must be zero?
Original post by dextrous63
Why do you think that x=0 is not accepted as a valid solution? (Hint - recall your log knowledge).
In which case, what must make y=0?

Due to the asymptote at x=0?
Original post by That_Guy_Omzz
Due to the asymptote at x=0?

What is the domain (at A-level) of the ln function?
Original post by That_Guy_Omzz
Due to the asymptote at x=0?

Correct. However, since we now know x>0, as said in my edit, we can ignore considering x=0.

So, what must = 0?
Reply 8
Avatar for z4yn4
z4yn4
3
Remember that ln(1)=0
Therefore how do I get ln 1?
4/4 is 1
Meaning x is 4
You can ignore the x to the power of 5/2 since anything multiplied by 0 is 0
Reply 9
Avatar for mqb2766
mqb2766
21
Original post by z4yn4
Remember that ...

Hints not solutions pls.
See the sticky at the top of the forum
Thanks for the help everyone, I've got it:biggrin:

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