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C1 - coordinate geometry

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Reply 20
Avatar for zed963
zed963
16
Original post by Galileo Galilei
Mathematical logic


That's very helpful.
What exam board are you?
Original post by zed963
That's very helpful.


I am just kidding, I worked it out using the information given in the question
Reply 23
Avatar for zed963
zed963
16
Original post by Galileo Galilei
I am just kidding, I worked it out using the information given in the question


Explain please.
Reply 24
Avatar for H0PEL3SS
H0PEL3SS
12
Original post by zed963
That's very helpful.

He literally subbed x=p into the equation for l1.
Original post by Super199
How do I do part d? Any hints on how to start?
Thanks :smile:

I did this question, but I can't remember where, so if you could tell me the paper you're doing OP, that would be great.


Spoiler

Original post by zed963
Explain please.


Plug the value of P into the equation for L1 to find Y
If C has x-coordinate p, then it has y-coordinate -p/2 + 6.


Therefore: (A,C) = √((2 - p)^2 + (5 + p/2 - 6)^2) = 5,

√(4 - 4p + p^2 + (p/2 - 1)^2) = 5,

√(4 - 4p + p^2 + (p^2)/4 - p + 1) = 5,

√(16 - 16p + 4p^2 + p^2 - 4p + 4)/2 = 5,

√(5p^2 - 20p + 20) = 10,

5p^2 - 20p + 20 = 100,

p^2 - 4p + 4 = 20,

p^2 - 4p - 16 = 0.


Hope this helps
Reply 27
Avatar for zed963
zed963
16
Original post by H0PEL3SS
He literally subbed x=p into the equation for l1.

I did this question, but I can't remember where, so if you could tell me the paper you're doing OP, that would be great.


Spoiler



Your working out makes sense.
Reply 28
Avatar for zed963
zed963
16
Original post by BuddingAchiever
If C has x-coordinate p, then it has y-coordinate -p/2 + 6.


Therefore: (A,C) = √((2 - p)^2 + (5 + p/2 - 6)^2) = 5,

√(4 - 4p + p^2 + (p/2 - 1)^2) = 5,

√(4 - 4p + p^2 + (p^2)/4 - p + 1) = 5,

√(16 - 16p + 4p^2 + p^2 - 4p + 4)/2 = 5,

√(5p^2 - 20p + 20) = 10,

5p^2 - 20p + 20 = 100,

p^2 - 4p + 4 = 20,

p^2 - 4p - 16 = 0.


Hope this helps


Can you explain that?
Reply 29
Avatar for Super199
Super199
OP
20
Original post by H0PEL3SS
He literally subbed x=p into the equation for l1.

I did this question, but I can't remember where, so if you could tell me the paper you're doing OP, that would be great.


Spoiler


Jan 2009 :smile:. I've solved it now so all good. One more question I couldn't do was part c. Any hints on how to do this?
I can't seem to work it out.
c1- series.jpg43.0KB
2014-04-16 20.29.39.jpg

My solution.
2014-04-16 20.29.39.jpg248.2KB
Original post by Super199
Jan 2009 :smile:. I've solved it now so all good. One more question I couldn't do was part c. Any hints on how to do this?
I can't seem to work it out.


Draw a triangle and think about it
Reply 32
Avatar for Super199
Super199
OP
20
Original post by Galileo Galilei
Draw a triangle and think about it

Using n2(2a+(n−1)d\frac{n}{2}(2a+(n-1)d I can't seem to get it into that form. :s-smilie:
Reply 33
Avatar for Super199
Super199
OP
20
Original post by Galileo Galilei
But that isnt Q10 C? Which question are you talking about?

This one haha
c1- series.jpg43.0KB
Original post by Super199
This one haha


Got ya, do you want the solution or hints mate?
Reply 35
Avatar for Super199
Super199
OP
20
Original post by Galileo Galilei
Got ya, do you want the solution or hints mate?

A solution I guess. I mean I know what to do but I can't seem to get it in that form.
Reply 36
Avatar for H0PEL3SS
H0PEL3SS
12
Original post by Super199
Using n2(2a+(n−1)d\frac{n}{2}(2a+(n-1)d I can't seem to get it into that form. :s-smilie:

Just find an expression for n using the sum formula. You should double 2750 to get rid of the n/2. From there, expand and simplify.
For part C, take the equation of sum of n

n/2(2a+(n-1)d)
then substitute numbers

n/2(-17.5(2)+2.5n-2.5)=2750

times 2750 by 2

n(-35+2.5n-2.5)= 5500

expand
-35n+2.5n^2-2.5n=5500

times by 2

-75n+5n^2=11000
5n^2-75n-11000=0
n^2-15n-2200=0

Therefore

n^2-15n-55x40
Original post by BuddingAchiever
For part C, take the equation of sum of n

n/2(2a+(n-1)d)
then substitute numbers

n/2(-17.5(2)+2.5n-2.5)=2750

times 2750 by 2

n(-35+2.5n-2.5)= 5500

expand
-35n+2.5n^2-2.5n=5500

times by 2

-75n+5n^2=11000
5n^2-75n-11000=0
n^2-15n-2200=0

Therefore

n^2-15n-55x40



you can just check that 55x40=2200....if you can't do this question, at least you will be able to do part d
Reply 39
Avatar for zed963
zed963
16
Original post by Super199
A solution I guess. I mean I know what to do but I can't seem to get it in that form.


ImageUploadedByStudent Room1397677854.500249.jpg


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