Shewing that a function attains every value.
117418
Showing that the image of a function is $\mathbb{C}$ if it satisfies a nice functional equation
97020
Idiom for doing anything to get what you want
98559
subtlety of self-defined function and its evaluation
727
Prove that any continuous integer-valued function of a real variable is constant.
105172
Prove that the entire function is constant over certain conditions.
50111
non-continuous function satisfies $f(x+y)=f(x)+f(y)$
125788
A function with a property $f(x+y)=f(x)f(y)$
86128
Find all functions $ f : \Bbb R \to \Bbb R$ which satisfy $f(x)f(y) = f(x + y) + xy$ for all $x, y ∈ \Bbb R$.
79925
Infinitely many values of $x$ that satisfy the equations
65946
A function $f: \mathbb R \to \mathbb R$ satisfies equation $f(x+y)=f(x)f(y)$ for all $x,y\in \mathbb R $
10181
Entire one-to-one functions are linear
132730
Is there an everywhere discontinuous increasing function?
84317
Iterated self-composition of arbitrary function
102075
A function continuous on all irrational points
144323
Differentiation of a function
133837
Entire function dominated by another entire function is a constant multiple
57938
When do two functions become equal?