Question

Question 5 Find the equation of the circle with centre (–a, –b) and radius (a^2 - b^2)^0.5

Class X1 - Maths -Conic Sections Page 241

Answer 1

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Answer 2

concept :- if centre (P, Q) and radius r are given then equation of circle is (x-P)² +(y-Q)²=r²

here,
centre = (-a, -b)
radius = √(a² - b²)

so, equation of circle is
{x - (-a)}² + {y - (-b)}² = {√(a² - b²)}²
(x + a)² + (y + b)² = a² - b²
x² + a² + 2ax + y² + b² + 2by = a² - b²
x² + y² + 2ax + 2by + 2b² = 0

hence, equation of circle is , x² + y² + 2ax + 2by + 2b² = 0