answer:
(a).
Equation of circle is x² + y² - 25 = 0
(b).
(-5, 0) » yes
(√7, 1) » no
(-3, √21) » no
(0, 7) » no
Step-by-step explanation:
(a).
If centred at origin, centre is (0, 0)
General equation of circle:
[tex]{ \boxed{ \bf{ {x}^{2} + {y}^{2} + 2gx + 2fy + c = 0}}}[/tex]
but g and f are 0:
[tex] {x}^{2} + {y}^{2} + c = 0 \\ but : \\ c = {g}^{2} + {f}^{2} - {r}^{2} \\ c = { - 25} [/tex]
