Write an equation of the circle with center (5, -7) and radius 9.

(x - 5)² + (y + 7)² = 81

Step-by-step explanation:

The equation of a circle in standard form is

(x - h)² + (y - k)² = r²

where (h, k) are the coordinates of the centre and r is the radius

Here (h, k) = (5, - 7) and r = 9, thus

(x - 5)² + (y - (- 7))² = 9², that is

(x - 5)² + (y + 7)² = 81 ← equation of circle

56.6

step-by-step explanation:

the ratio of the perimeters is equal to the scale.

the ratio of the areas is equal to the square of the scale.

34 / 20 = k

a / 19.6 = k²

substituting:

a / 19.6 = (34 / 20)²

a = 19.6 (34 / 20)²

a ≈ 56.6