# The equation of a circle is (x + 7)^2 + (y + 2)^2 = 49. How do you determine the length of the diameter?

Apr 2, 2016

$d = 14$

#### Explanation:

For circles in general,

${x}^{2} + {y}^{2} = {r}^{2}$

is true.

The equation above is already solved by completing the square, and is in the form above.

Therefore, if

${r}^{2} = 49$

Then,

$r = \sqrt{49}$
$r = 7$

But this is only the radius. If you want the diameter, multiply the radius by two and get the whole way across the circle.

$d = 2 \cdot r = 14$