[tex]\it f(x)=x+3\\ \\ 2f(x)+f(2)\geq4f(1) \Rightarrow 2(x+3)+2+3\geq4(1+3)\Rightarrow 2x+6+5\geq16 \Rightarrow\\ \\ \Rightarrow 2x+11\geq16|_{-11} \Rightarrow2x\geq5|_{:2} \Rightarrow x\geq\dfrac{5}{2} \Rightarrow x\in\Big[\dfrac{5}{2},\ \infty\Big)[/tex]
