The equation of circle with centre (1, -2) and radius 4 cm is :

We know that,

(x -a)² + (y - b)² = radius²

Here, a and b are point on centre

x and y be any point on circle

We have,

Centre point are  (1, -2)

Radius = 4cm

Put the value of  a, b and radius in the above formula,

(x-1)² + (y + 2)²  = 16

= x² + 1 - 2x + y² + 4 + 4y = 16

= x² + y² - 2x + 4y = 11