Practice problem
Let f:R→Rf: \mathbb{R} \to \mathbb{R}f:R→R be a function. Which of the following is always true?
If a=ba = ba=b, then f(a)=f(b)f(a) = f(b)f(a)=f(b).
For any yyy, there exists xxx such that f(x)=yf(x) = yf(x)=y.
If f(a)=f(b)f(a) = f(b)f(a)=f(b), then a=ba = ba=b.
Type a concept, like “slope” or “photosynthesis”.