Question

Need help quick, please?

Answer 1

Remember that the general formula for a circle is  
(x – h)² + (y – k)² = r², where (h,k) is the coordinate of the center. 
We already know that (h,k) = (5,-4), since we know the center's coordinates. We need to find r, the radius, using the distance between the center and the point (-3,2). 
To do this, we can either use the distance formula, or plug in the points in our circle equation and solve for r.
Let's do the second one, plugging in and solving for r.
We can use the point (-3,2) for (x,y):
(x – h)² + (y – k)² = r²
(-3 - 5)² + (2 - -4)² = r²
(-8)² +(6)² = r²
64 + 36 = r²
100 = r²
r = 10
We know that r=10, and that r² = 100
Using h, k, and r, we can now solve for the equation of the circle in standard form.
The equation of the circle is:
(x – 5)² + (y + 4)² = 100