Question

how is uniqueness expressed?​

Answer 1

Answer:

Existence: f(x)=x2+3 works. Uniqueness: If f0(x) and f1(x) both satisfy these conditions, then f′0(x)=2x=f′1(x), so they differ by a constant, i.e., there is a C such that f0(x)=f1(x)+C. ... This is usually accomplished by proving ∀x(P(x)⇔x=x0), where x0 is some particular value. Example 2.5.