# How do you write an equation in standard form of the circle with the given properties: endpoints of a diameter are (9,2) and (-9,-12)?

##### 1 Answer

#### Explanation:

The diameter length will be the distance between (9,2) and (-9,-12)

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Known: The equation of a circle where the centre is coincidental to the origin is

But the centre of the circle does not coincide with the origin.

So the equation needs to be adjusted. We have to make allowance for offsetting both the x and y.

Centre of the circle is at the mean x and the mean y

Centre

So we need to 'translate' (mathematically move) the coordinates of the circles centre back to the origin to relate it to

Consider

Please ignore the red dotted lines. My package is doing something odd!