Maths Question

montown

Trying to do this project maths question, wrecking my head even though i know its something simple that I'm missing!

the line X+3y=20 intersects the circle x^2 + y^2 -6x -8y=0 at the points P and Q. Find the equation of the circle that has PQ as diameter.

So far I've worked out the radius of the circle as 3root10 /2 but I can't get the centre for the life of me.

Anyone else finding it really annoying that we don't have access to solutions for these stupid questions? An answer at the back of the book does not help! 100% going to fail paper 2 for the mocks.

Neodymium

the centre is the midpoint between P and Q

montown

Neodymium wrote: »

the centre is the midpoint between P and Q

I don't have values for P and Q?

Moody_mona

montown wrote: »

Neodymium wrote: »

the centre is the midpoint between P and Q

I don't have values for P and Q?

But you can find them. You need to use simultaneous equations.

deand21594

i hate project maths, giving me all sorts of problems

Blink182rock

If you still want the answer I can show you how to do it ??

finality

x = 20 - 3y

sub that into the equation of the circle, you'll get a trinomial, solve for the two points of intersection, and get the midpoint of those two points, that's your centre.

Blink182rock

the use distance formula to get the distance from one of the points to the centre and that gives you the radius...
sub in all the info into the (h,k) equation and bobs your uncle!!

lostatsea

This question has nothing to do with the new approach in Project Maths. It could easily have been asked on the old course.