Greetings!
Answer:
(x + 3)² + ( y - 1)² = 81
Step-by-step explanation:
To go in reverse, you need to remember that in the equation:
(x - a)² + (y - b)² = r²
a is the x coordinate of the centre and b is the y coordinate of the centre.
As -3 is the x coordinate, we can replace a with 3, and then replace b with 1:
(x - -3)² + (y - 1)² = r²
The two negatives change to a positive:
(x + 3)² + ( y - 1)² = r²
If r is already given as 9, r² is simply 9²
(x + 3)² + ( y - 1)² = 9²
(x + 3)² + ( y - 1)² = 81
So the equation of the circle is (x + 3)² + ( y - 1)² = 81
Hope this helps!
