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# AQA A2 Mathematics MPC4 Core 4 - 9th June 2015 [Discussion & unofficial markscheme] watch

1. (Original post by Stepidermis)
There must be other ways of showing that y=0, however in this instance I don't think your way works because in the question they have told you that q cannot equal 0 but they haven't given you a restriction for p (correct me if I'm wrong).

So the fact that you've found two equivalent expressions for x in this case is nullified by the fact that they both contain (q/p), as if p=0 then they don't intersect as this would instead be an asymptote, does that make sense?
I see! Argh how I hate some of these questions that contradict everything I thought I knew... 😭

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2. (Original post by CD223)
I see! Argh how I hate some of these questions that contradict everything I thought I knew... 😭

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Well actually I think I'm being a bit overscrupulous here as I doubt the mark scheme will be THAT picky, so you'll probably get the marks anyway, just thought I'd show you a more efficient approach is all...

*walks away*

3. (Original post by Stepidermis)
Well actually I think I'm being a bit overscrupulous here as I doubt the mark scheme will be THAT picky, so you'll probably get the marks anyway, just thought I'd show you a more efficient approach is all...

*walks away*

Your approach makes more sense! It's just frustrating that what I thought was right could be wrong if p was zero :L

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4. (Original post by CD223)
Ever so sorry, I thought you needed help with 3c and not 3b. Here's my method for both parts.

Attachment 408151

Is this correct?

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yep that is correct!

but what I don't understand is how finding the dot product of pq and qr will help me find angle q?

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5. (Original post by the_googly)
yep that is correct!

but what I don't understand is how finding the dot product of pq and qr will help me find angle q?

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The dot product helps you find the angle between two lines.

Hopefully this clears it up

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6. (Original post by CD223)
Oh right thanks!

Is this an acceptable way of showing the two tangents meet on the x axis?

(Jan 13 Q4 a ii)

Attachment 410827

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I would have thought so. But I'm not too sure.
7. (Original post by a123a)
I would have thought so. But I'm not too sure.

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8. Hi can anybody tell me why on Jan 11 Q8 b(ii), when you get two values for mu, you're supposed to choose mu=5/7 and not mu=1 ? I've been trying for a while now and i can't understand why Sorry if this has already been covered; here's the paper/markscheme, thanks

http://filestore.aqa.org.uk/subjects...W-QP-JAN11.PDF
http://filestore.aqa.org.uk/subjects...W-MS-JAN11.PDF
9. Can somebody check my working for question six. can't seem to get around it

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Attached Images

10. (Original post by CD223)
The dot product helps you find the angle between two lines.

Hopefully this clears it up

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thanks

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11. Think I've done it properly

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Attached Images

12. (Original post by the_googly)
Think I've done it properly

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Here's my workings for the same questions.

I believe our answers agree, even though they're expressed slightly differently

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13. (Original post by CD223)
Here's my workings for the same questions.

I believe our answers agree, even though they're expressed slightly differently

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your way seems much better and more convincing. :-)

how are you revising now for this exam?

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14. (Original post by the_googly)
your way seems much better and more convincing. :-)

how are you revising now for this exam?

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Just purely past papers! How about you?

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15. (Original post by CD223)
Just purely past papers! How about you?

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will be starting past papers tomorrow!

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16. (Original post by CD223)
Could someone explain where I've gone wrong on June 2010 Q7?

Attachment 409213

I've set up a quadratic in terms of like so:

To which the solutions are:
or

This gives co ordinates of C as:
which is correct, and which is incorrect.

How can I get to the other possibility of ?

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Hey I don't know if anyone gave a solution for this but I think it may be because in your second parallelogram BP isn't parallel to AC due to C being in a different position so the equation is only valid for one solution if that makes sense? Sorry if this is wrong or someone already answered it!
17. (Original post by the_googly)
will be starting past papers tomorrow!

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Oh nice have you not done any yet?

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18. (Original post by Baloney26)

Hey I don't know if anyone gave a solution for this but I think it may be because in your second parallelogram BP isn't parallel to AC due to C being in a different position so the equation is only valid for one solution if that makes sense? Sorry if this is wrong or someone already answered it!

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19. (Original post by CD223)

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No problem 😊.
20. (Original post by Baloney26)
No problem 😊.

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