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

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Answer 1 · 2016-04-02T17:27:56

$d = 14$ $d = 14$

For circles in general,

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

is true.

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

Therefore, if

$r^{2} = 49$ $r^2 = 49$

Then,

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

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

$d = 2 \cdot r = 14$ $d = 2*r = 14$

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