Equation from Three Points*HELP*
posted by Adrianna on .
Write the standard equation for the circle that passes through the points:
(0, - 8)
You must include the appropriate sign (+ or -) in your answer. Do not use spaces in your answer.
x 2 + y 2 x y = 0
HELP PLEASE I NEED STEP BY STEP EXPLANATION!!
I KNOW THAT THE FORMULA IS =
I JUST DON'T GET IT AND NEED SERIOUS EXPLANATION.
Use this standard circle equation:
(x-a)^2 + (y-b)^2 = c^2
Your three points tell you that:
a^2 + b^2 = c^2
(6-a)^2 + b^2 = c^2
a^2 + (b+8)^2 = c^2
The first two of these equations combine to give:
6-a = +or- a . Only + sign works.
a = 3
The first and third equations combine to give
b + 8 = +or- b
Only - sign works.
b = -4
c^2 = a^2 + b^2 = 25
c = +or- 5
So the equation that fits them all is
(x-3)^2 + (y+4)^2 = 25