Respuesta :
A circle is a curve sketched out by a point moving in a plane. For the given equation of a circle, the centre will lie at the coordinate (7,-4), while the radius will be equal to 9 units.
What is the equation of the circle with radius r units, centred at (x,y)?
A circle is a curve sketched out by a point moving in a plane so that its distance from a given point is constant; alternatively, it is the shape formed by all points in a plane that are at a set distance from a given point, the centre.
If a circle O has a radius of r units length and it has got its centre positioned at (h, k) point of the coordinate plane, then, its equation is given as:
(x-h)² + (y-k)² = r²
Given the equation of the circle is (x-7)²+(y+4)²=81. The equation can be rewritten as,
(x-7)² + [y-(-4)]² = 9²
Hence, For the given equation of a circle, the centre will lie at the coordinate (7,-4), while the radius will be equal to 9 units.
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