QuestionIdentify the center and radius of these circles and find the standard form for given conditions.
1. $x^{2}+y^{2}=49$
2. $5 x^{2}+5 y^{2}=125$
3. $(x+4)^{2}+(y-2)^{2}=9$
4. center at origin, radius $5 \sqrt{3}$
5. center at $(17,5)$, radius 12
6. center at $(-8,4)$, contains $(-4,2)$
7. center at $(15,7)$, tangent to $x$-axis.