ПОМОГИТЕ СО ВТОРЫМ!!!СРОЧНО

Решите задачу:

$1)\; \; f(x)=5+|x|\\\\|x|\geq 0\; \; \to \; \; 5+|x|\geq 5\; \; \to \; \; f(x)\in [\, 5,+\infty )\\\\2)\; \; f(x)=\sqrt{1-x^2}\\\\y=\sqrt{1-x^2}\geq 0\\\\y^2=1-x^2\; ,\; x^2+y^2=1\; \; okryznost,\; centr\; (0,0),\; R=1\\\\1-x^2\geq 0\; ,\; \; x^2-1\leq 0\; ,\; (x-1)(x+1)\leq 0\; \to \; \; x\in [-1,1\, ]\; \Rightarrow \\\\0\leq f(x)\leq 1\; \; ,\; \; f(x)\in [\, 0;1\, ]\\\\3)\; \; f(x)=\frac{1}{x^2+1}\\\\x^2\geq 0\; \; \Rightarrow \; \; x^2+1\geq 1\; \; \to \; \; \frac{1}{x^2+1}\leq 1\\\\f(x)\in (0,1\, ]$