find an equation of the circle that has center (2,-4) and passes through (-1,-2)

Answer 1

(x - 2)² + (y + 4)² = r²

Find r² by using the distance formula for the distance between (-1,-2) and (2,-4).

r² = (-1 - 2)² + (-2 + 4)² = ?

You can finish from here.