Step-by-step explanation:
A circle equation is represented by
[tex]x {}^{2} + {y}^{2} = r {}^{2} [/tex]
A circle have both terms to the 2nd. degree
The 1st equation, 2nd equation, 4th equation are circles.
A quadratic is represented by
[tex] {x}^{2} + bx + c[/tex]
A quadratic equation only has one term that is second degree.( meaning if x and y are both to the 2nd degree, it will not be a quadratic, it will be a circle.
The 3rd equation is a quadratic.
The fifth equation has a leading coefficient at the degree of 1 so it is other(linear)