Why are my answers wrong?

1) A quadratic equation in two variables always have two possible solutions in any number system.

My answer: False, it has no solution when a = 0.

2) All equations in two variables, such that both variables have maximum exponent as 2 and minimum as zero represents an equation of a circle.

My answer: False, in equation of a circle, when exponent is 0, (x-h)^0+(y-k)^0=r^2 is not a circle

3) Find the composition of the function as indicated, find domain of composite function and explain your answer(s).

f(x) = ( (4x^2) - 2) / (-4 + 8x)

g(x) = ( (9x^2) -9) / (-12+6x)

Find fog and fof