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# C2 Coordinate geometry

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1. Here are the questions:

1) The points A(-3,19), B(9,11) and C(-15,1) lie on the circumference of a circle. Find the coordinates of the centre of the circle.

Midpoint = (-3+9/2, 19+11/2) = (-3,15)

11-19/9+3 = -3/4

4y=-3x+51

Did the same for the other one, and got: M.P.(9,10) and 2y=3x-7

(4y=-3x+51) + (2y=3x+7) -> 6y=44 -> y=44/6=22/3

Is this right so far?

2) Find the distance between (-4a,0) and (3a,-2a)

d=√[(3a+4a)2+(-2a-0)2]
=√[(7a)2+(-2a)2]
=√[49a2+4a2 = √53a2

Would the answer be √53a or 53a?
2. It is 53a, because the square root cancels out with the squared. Remember it is .
3. Sqrt{53}
4. (Original post by Math12345)
It is 53a, because the square root cancels out with the squared. Remember it is sqrt(53a)^2
No it isn't

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