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

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Answer 1 · 2016-04-02T17:27:56

#d = 14#

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*r = 14#