How do you write an equation of a circle with center at (-2,-8), r=5?

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Answer 1 · 2017-01-16T03:01:12

$(x + 2)^2 + (y + 8)^2 = 25$

The standard equation of a circle is shown as below:

$(x - h)^2 + (y - k)^2 = r^2$

$(h,k)$ represents the center of the circle.

In this situation, the center is $(-2, -8)$ . To figure out the circle's equation, you must plug in the numbers to their respective variables.

$(x - (-2))^2 + (y - (-8))^2 = r^2$

Double negatives will give you a positive number, so the equation will simplify into:

$(x + 2)^2 + (y + 8)^2 = r^2$

The radius of the circle is 5, so the number should be inserted into the $r$ variable, like so:

$(x + 2)^2 + (y + 8)^2 = 5^2$

Finally, simplify 5^2, and you'll end up with the equation of the circle.

$(x + 2)^2 + (y + 8)^2 = 25$