On the exam I was asked the question about Transcritical bifurcation. I gave the equation
$$ \dot x = rx - x^2 $$
Then I was asked why it is not a differential equation and I couldn't answer. I thought if some derivative equals a function - it is a differential equation.
It's not a differential equation, because r is a variable not x?*
*Sorry If something is not clear. I suffer for lack of math in english.