What are the domains of the fraction expressions?

a) [[$ \displaystyle\frac {x} {4x^2 - 16x} $]]

Answer: The fraction expression is defined when [[$ x $]] ≠ and [[$ x $]] ≠ .

b) [[$ \displaystyle\frac {x} {5x^2 - 25} $]]
Answer: The fraction expression is defined .