Circle / radius question (3 marks) ????

Can you show me how to answer this?



I know the forumla

(x-h)^2 + (y-k)^2 = r^2



Thanks.

1. Complete the square for X and Y.

2. Simultaneous equations

First rearrange the equation so that it looks like (x-h)^2 + (y-k)^2 = r^2. I find the easiest method is to use 'completing the square'.

I know you have to complete the square and I have put it in the form

x^2-2x + y^2 - 4y - 20 = 0

But how do I do that?

All the videos I have seen for it are for totally different non related questions.

Here is some clue

Let me know if you want more help

How did you get $(x-1)^2-1$
And $(y-2)^2-4$
in the first place?

Well, let's take the x's for example. We want to complete the square of $x^2-2x$

To do this, I put (x - half of the coefficient of x from the above equation), and squared. $(x-1)^2$ but, this equals $x^2-2x+1$ so I added -1 on the end to make them equal repeat process

Oh yeah I remember now Will do that!

Ok lets go back a step

Can you complete the square

Can you re-write $x^2 + 4x - 5$

in the form $(x+a)^2 + b$

Then try and use substitution for ii)

Got it now! U had to use trigonometry; I htought it was some common sense thing

How do I do part ii) Can you go through it? THanks!

You know that y=x+2 so just sub it in to the equation you found after having completed the square. That should work out pretty nicely

Got it now! U had to use trigonometry; I htought it was some common sense thing

Then try and use substitution for ii)

Ok lets go back a step

Can you complete the square

Can you re-write $x^2 + 4x - 5$

in the form $(x+a)^2 + b$

Ok so I found A and B for part ii) And C from part i)

How do I do part iii) ?

Thanks!

sine my brutha!

Yeah I know SOH sine etc

but how do i get there?

a = (4,6) b = (-3,-1) c = (1,2)