[tex]\displaystyle\\x = 45\\\\y = 4x + \sqrt{x} + 0.2 - 5x\\\\y = 4\cdot45 + \sqrt{45} + 0.2 - 5\cdot45\\\\y = 180 + \sqrt{9\cdot5} + 0.2 - 225\\\\y = 180 + 3\sqrt{5} + 0.2 - 225\\\\y = 180 - 225 + 0.2 + 3\sqrt{5}\\\\y = -45 + 0.2 + 3\sqrt{5}\\\\\boxed{\bf y = -44.8 + 3\sqrt{5}}[/tex]
