You are Here: Home >< Maths

# Edexcel FP1 14/05/2015 - Question 8. watch

1. This years paper was generally a nice paper, we had an easy matrices proof by induction and we barely scratched the surface of summing a series. I got to the final question with 30 minutes to spare.

However, Question 8 was a joke, here is the question:

y^2= 12x, the point P is at point P(3p^2, 6p)

S is the focus

a) Show that SP is 3(1+p^2)

Q= (3q^2, 6q) p=/=q

b) The tangent at point P on the curve and the tangent of point Q on the curve meet at point R, find the coordinates of the point R

c) Show that RS= SP.SQ
________________________________ ________________________

Part a) was fine, if you didn't know you had to Pythagoras the change in x and change in y and simplify.

Part b)

I was stuck on this question, like no method I tried seemed to work right, I would always get p=q.

First, I found the equation of the tangent: y = 1/p x + 3p

Then subbed in q (Coords were the same algebraicly) y= 1/q x +3q

then I'm stumped.

Normally you would sub in the values of the point into the y and x variables and solve a quadratic equation, this time, there is no such luck.

I tried to sub in the y value and eliminate a variable: Nope.

I tried to sub in an x value and eliminate a variable: Nope

Were you supposed to sub in x = y^2 /12 ?, I'm honestly concerned that I'm just forgetting something.

Edit: EDEXCEL ARE NOT NICE PEOPLE.

You basically had to equate one another and get x/y on its own.

I could have sworn the question didn't specify for an answer in terms of p and q, I was trying to find their values....

2. (Original post by XI Ki11JoY IX)
This years paper was generally a nice paper, we had an easy matrices proof by induction and we barely scratched the surface of summing a series. I got to the final question with 30 minutes to spare.

However, Question 8 was a joke, here is the question:

y^2= 12x, the point P is at point P(3p^2, 6p)

S is the focus

a) Show that SP is 3(1+p^2)

Q= (3q^2, 6q) p=/=q

b) The tangent at point P on the curve and the tangent of point Q on the curve meet at point R, find the coordinates of the point R

c) Show that RS= SP.SQ
________________________________ ________________________

Part a) was fine, if you didn't know you had to Pythagoras the change in x and change in y and simplify.

Part b)

I was stuck on this question, like no method I tried seemed to work right, I would always get p=q.

First, I found the equation of the tangent: y = 1/p x + 3p

Then subbed in q (Coords were the same algebraicly) y= 1/q x +3q

then I'm stumped.

Normally you would sub in the values of the point into the y and x variables and solve a quadratic equation, this time, there is no such luck.

I tried to sub in the y value and eliminate a variable: Nope.

I tried to sub in an x value and eliminate a variable: Nope

Were you supposed to sub in x = y^2 /12 ?, I'm honestly concerned that I'm just forgetting something.
i got same for equations. then i equated p equation with q equation as got we both got it in terms of y =. then solved to get x co ordinates ?
3. If y=(1/p)X+3p and y=(1/q)X+3q, then just equate them to each other, so (1/p)X+3p=(1/q)X+3q, the solve for X. Afterwards, put the tangent equations as x in terms of y (e.g. x=py-3p^2) and equate them to each other again to find the value of y.
4. The tangent lines are and . Make the subject of each and equate both of them to get . Then do the same for and you get .
5. Part (a) I don't think required any real calculation - all did was to add 3 to the x coordinate of P (to find distance of P from the directrix). This gives you 3p^2 + 3 [aka 3(p^2+1)], which we know from the definition of a parabola to be the same as the distance SP.
Regretting not putting more down.
6. (Original post by Don John)
The tangent lines are and . Make the subject of each and equate both of them to get . Then do the same for and you get .
i left the equations as the original post. therfore i got x being -3(q-p)^2 ?
7. is this edexcel gcse maths
8. (Original post by Maths degree)
i left the equations as the original post. therfore i got x being -3(q-p)^2 ?

9. (Original post by Don John)

Literally realised that before going to sleep last night lol, I feel stupid.
10. (Original post by XI Ki11JoY IX)
Literally realised that before going to sleep last night lol, I feel stupid.
I think anyone that thought over any questions they struggled with (uauslly 8c) realised how to do it before going to sleep... I did... shame it was a bit late So don't feel stupid. It happens to everyone.
11. (Original post by Tiva4Eva)
I think anyone that thought over any questions they struggled with (uauslly 8c) realised how to do it before going to sleep... I did... shame it was a bit late So don't feel stupid. It happens to everyone.
I can't remember 8c, never mind though, I'm still looking for a high B

### Related university courses

TSR Support Team

We have a brilliant team of more than 60 Support Team members looking after discussions on The Student Room, helping to make it a fun, safe and useful place to hang out.

This forum is supported by:
Updated: May 15, 2015
Today on TSR

### Edexcel C4 Maths Unofficial Markscheme

Find out how you've done here

### 1,065

students online now

Exam discussions

Poll
Useful resources

### Maths Forum posting guidelines

Not sure where to post? Read the updated guidelines here

### How to use LaTex

Writing equations the easy way

### Study habits of A* students

Top tips from students who have already aced their exams