Question

The equation of the circle which passes through the point (4, 5) and has its centre at (2, 2) is ____________.

Answer 1

Circle with center (2, 2) has equation of the form (x – 2)² + (y – 2)² = r² (1)
Since circle passes through (4, 5)
⇒ (4 – 2)² + (5 – 2)² = r²
i.e. 2² + 3² = r²
i.e. 4 + 9 = r²
i.e. r² = 13
i.e. equation of circle is (x – 2)² + (y – 2)² = 13.