If $f:R\rightarrow R$ is defined as $f(x)=6^x+6^{|x|}$ then what type of function is $f$ ?

Question

$\begin{array}{1 1} \text{1-1 not onto} \\ \text{onto but not 1-1} \\ \text{both 1-1 and onto} \\ \text{neither 1-1 nor onto} \end{array}$