Răspuns :
[tex]\it f(x)=2x+3\ \ \ \ \ \ (*)\\ \\ f(x)=-9\ \stackrel{(*)}{\Longrightarrow}\ 2x+3=-9|_{-3} \Rightarrow 2x=-12|_{:2} \Rightarrow x=-6[/tex]
[tex]\it f(x)=2x+3\ \ \ \ \ \ (*)\\ \\ f(x)=-9\ \stackrel{(*)}{\Longrightarrow}\ 2x+3=-9|_{-3} \Rightarrow 2x=-12|_{:2} \Rightarrow x=-6[/tex]