help

No! I am not winding you up! dont worry

But yea, I know that... but where do I get these numbers?!! there are no coordinates in the question or anything?? Eugh, i give up on this, ill move onto the next question on the book...

Ok, I will tell you the answer - not that it's going to help you.

For the circle to 'touch' each axis we must have that the centre point of the circle is of the form $(a,b)$ where $a=b$

Since we also have that $(a,b)$ lies on the line $y=3x-4$ we must have $b=3a-4$ but we also know that $a=b$, so $a = 3a -4$ gives the centre of the circle being $(2,2)$ now the radius is also obvious.

I understand it now, that was more helpful than all the other posts combined.

Thanks

Ok, I will tell you the answer - not that it's going to help you.

For the circle to 'touch' each axis we must have that the centre point of the circle is of the form $(a,b)$ where $a=b$

Since we also have that $(a,b)$ lies on the line $y=3x-4$ we must have $b=3a-4$ but we also know that $a=b$, so $a = 3a -4$ gives the centre of the circle being $(2,2)$ now the radius is also obvious.

why are we allowed to set b equal to 3a-4?

No it wasn't. You think it was helpful because I told you the answer, you need to learn to think for yourself - you're going to be royally screwed in AS Maths exams in all honesty.

Because it lies on the line y=3x-4

Can you find a relationship between (1,1) ; (2,2) ; (3,3) ... (n,n)?

yep, the x and y coordinates are equal distance from the axis

But I now understand it as you showed me how to arrive at the answer, I have thought about it

Yes, but this was for a specific case, unless you get the identical question, you're probably not going to know how to do it. How about this, it's essentially the exact same question:

"A circle touches the negative y-axis and the negative x-axis and it's centre lies on the line y=5x+7. What is the equation of the circle?"

b=5a+7 but since they are equal distance form the axis then a=5a+7 therefore a=-7/4 and b=-7/4


job done

Where's the equation of the circle?

Where's the equation of the circle?

My turn for questions...

Why is it an equal distance from both sets of axis? (x=y)

The centre isn't the origin?

Because it just touches both axes, so the centre point must satisfy x=y, otherwise the circle would 'overhang' one of the axes, or not touch it.

oh, it lies on them?

I thought it just crossed over it like one tiny part of it

Generally when it says 'touches' it means just at one point.

Generally when it says 'touches' it means just at one point.

Was the equation right?

do you mind asking me some more c2 circle questions? I just find I try a lot harder in them if I am doing them for someone else... only if you don't mind