[tex]\displaystyle\bf\\a)\\\\y=\frac{2x-4}{10-2,\!5x}\\\\10-2,\!5x\neq 0\\\\2,\!5x\neq10\\\\x\neq\frac{10}{2,\!5}\\\\x\neq4\\\\x\in R-\{4\}\\\\y:R-\{4\}\to R\\\\\\b)\\\\y=\sqrt{x^2-196}\\\\x^2-196\geq 0\\\\x^2\geq 196~~\Big|\sqrt{~}\\\\\implies x \geq 14~~sau~~x\leq -14\\\\x\in (-\infty,~-14]~\bigcup~[14,~+\infty)\\\\y:(-\infty,~-14]~\bigcup~[14,~+\infty)\to R[/tex]
