Define $G: \mathbb R \to \mathbb R$ by the rule $G(x) = 2 − 3x$?

Question

Define $G: \mathbb R \to \mathbb R$ by the rule $G(x) = 2 − 3x$ for all real numbers $x$. Is $G$ onto? Prove or give a counterexample.

this from topic : One-to-One and Onto Functions.

Answer 1

If $y_0 \in \mathbb R$, is there some $x_0 \in \mathbb R$ such that $2-3x_0=y_0$ ?

If yes, then $G$ is onto, if no, then $G$ is not onto.