How write an equation for a circle using 8x +x^2 - 2y = 64 - y^2

see explanation

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

Given

8x + x² - 2y = 64 - y²

Collect the x/y terms, leaving 64 on the right side, that is

x² + 8x + y² - 2y = 64

To obtain standard form use the method of completing the square.

add ( half the coefficient of the x/y terms )² to both sides

x² + 2(4)x + 16 + y² + 2(- 1)y + 1 = 64 + 16 + 1

(x + 4)² + (y - 1)² = 81 ← in standard form

with centre (- 4, 1) and radius = 9

e.

step-by-step explanation:

because there are always 10 numbers in a phone number.