The Student Room Group

Coordinate geometry help - C2

60391a5d5c7a30737397f3d1904bd581.png

I know you have to get it into the formate (x-a)^2+(y-b)^2=r^2

Then you can work out the coordinates and use Pythagorus theorem to find out the radius


any help ?

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Reply 1
You seem to know the method, what have you done so far?
Original post by User32432432
60391a5d5c7a30737397f3d1904bd581.png

I know you have to get it into the formate (x-a)^2+(y-b)^2=r^2

Then you can work out the coordinates and use Pythagorus theorem to find out the radius


any help ?


Do you know how to complete the square?
Reply 3
Original post by raiden95
You seem to know the method, what have you done so far?

dont really know were to start
Reply 4
Original post by Mr M
Do you know how to complete the square?

yes sir
Reply 5
Original post by User32432432
dont really know were to start


Try completing the square using all terms with y as a start
Original post by User32432432
yes sir


Can you complete the square on this bit?

y26yy^2-6y
Reply 7
Original post by Fool In The Rain
If you put it in the form you mentioned, you should get:
x^2+(y-3)^2-7=0
That will give you your coordinates.

Then you expand the brackets, that will help you find the radius. (I'm not 100% sure though)


No this is wrong, give the OP a chance to try it
Original post by User32432432
60391a5d5c7a30737397f3d1904bd581.png

I know you have to get it into the formate (x-a)^2+(y-b)^2=r^2

Then you can work out the coordinates and use Pythagorus theorem to find out the radius


any help ?

complete square

arrange into circle equation format

take the square root of r^2

write down answer

Job done
Reply 9
Original post by Mr M
Can you complete the square on this bit?

y26yy^2-6y

(y-3y)^2 +9
Original post by User32432432
(y-3y)^2 +9


No that's very wrong.

Before you can tackle this question you need to go away and revise completing the square.
Reply 11
x2+bx=0.[br][br](x+b/2)2(b/2)2=0x^2 + bx = 0. [br][br](x+b/2)^2-(b/2)^2 = 0

Is this any help?
(edited 11 years ago)
Reply 12
Original post by raiden95
x2+bx=0.[br][br](x+b/2)2(b/2)2=0x^2 + bx = 0. [br][br](x+b/2)^2-(b/2)^2 = 0

Is this any help?

thats what I did ?
Reply 13
(x+b/2)2(b/2)2=0(x+b/2)^2-(b/2)^2 = 0
You didn't do that.

(x+bx/2)2+(b/2)2=0(x+bx/2)^2+(b/2)^2 = 0
You did this.
(edited 11 years ago)
Original post by raiden95
(x+b/2)2(b/2)2=0(x+b/2)^2-(b/2)^2 = 0
You didn't do that.

(x+b/2)2+(b/2)2=0(x+b/2)^2+(b/2)^2 = 0
You did this.


No he did this:

(x+b2x)2+(b2)2=0(x+\frac{b}{2} x)^2+(\frac{b}{2})^2 = 0
Reply 15
Original post by Mr M
No he did this:

(x+b2x)2+(b2)2=0(x+\frac{b}{2} x)^2+(\frac{b}{2})^2 = 0


Only just noticed:colondollar:
just complete the square
Reply 17
Original post by Mr M
No he did this:

(x+b2x)2+(b2)2=0(x+\frac{b}{2} x)^2+(\frac{b}{2})^2 = 0


Sorry for the late reply, is this correct ?
(y+3)^2+9y
Reply 18
Original post by User32432432
Sorry for the late reply, is this correct ?
(y+3)^2+9y


This is wrong, you need to look at completing the square in your maths text book
Reply 19
Original post by raiden95
This is wrong, you need to look at completing the square in your maths text book


Can you just explain what I have done wrong ?

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