λ ≠-17
λ ≠-18
λ ≠-19
λ ≠-20
(2 + 2λ + μ)x2 + (1 + 2λ + 2μ)y2 + (3 + 5λ + 3μ)xy
− (16 + 14λ + 11μ)x − (10 + 13λ + 17μ) + (24 + 20λ + 30μ) = 0 is an equation of circle only when