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# C1 - Coordinate Geo - Circle / Tangents Question

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1. Hi,

Got a question asking to find the points on the circle x^2 + y^2 - 6x -8y +15 = 0 cuts the y axis.

I know that means when x = 0.

I worked out the Centre of the circle by factorising to give C(3, 4) and the r^2 = 10

----
I can work out the correct values for y when x is 0 by taking y^2 - 8y +15 = 0 and testing values individually but I am unsure of the most efficient way to find the value of y.

Is anyone able to point me in the right direction so I can speed things up a bit if I get a question like this in the exam?

Thank you
2. (Original post by ghosteh)
I can work out the correct values for y when x is 0 by taking y^2 - 8y +15 = 0 and testing values individually but I am unsure of the most efficient way to find the value of y.
Do you know how to solve a quadratic equation?

is a quadratic equation in , factorise it to find the two solutions.
3. (Original post by Zacken)
Do you know how to solve a quadratic equation?

is a quadratic equation in , factorise it to find the two solutions.
OMFG

I am going delete this thread and then kill myself. Thank you
4. (Original post by ghosteh)
OMFG

I am going delete this thread and then kill myself. Thank you
Hahaha, don't worry, overlooking things happens to all of us.
5. (Original post by Zacken)
Hahaha, don't worry, overlooking things happens to all of us.
Thanks, I've calmed down a little now. Tried to rate you a point but since you're the last person I rated it won't let me haha
6. (Original post by ghosteh)
Thanks, I've calmed down a little now. Tried to rate you a point but since you're the last person I rated it won't let me haha
No problem.

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