Talk:Saddle-node bifurcation

I wonder under what conditions the product n_s*n_u is negative (zero!!) given that the factors are the numbers of exponents of in left and right half open planes?

This is a shorthand to say that \(n_s \neq 0\) and \(n_u \neq 0\) (both are obviously non-negative numbers).

This is obvious but misleading "math" formality for no reason.