$f : \mathbb{R} \to \mathbb{R}$ is $f(x) = \frac{2x + 3}{5}$. To show that $f$ is onto, which $x$ gives $f(x) = y$ for any real $y$?

Explanation

1. 01

   Solve $\frac{2x + 3}{5} = y$: $2x + 3 = 5y$, so $x = \frac{5y - 3}{2}$.

2. 02

   This $x$ is real for every real $y$, and $f(x) = y$, so $f$ is onto.