Найдите область определения функции:

Решите задачу:

$y= \sqrt{x-\frac{4}{x-3}} \\\\ \left \{ {{x-\frac{4}{x-3} \geq 0} \atop {x-3\ne 0}} \right. \; \left \{ {{ \frac{x^2-3x-4}{x-3} \geq 0 } \atop {x\ne 3}} \right. \; \left \{ {{ \frac{(x-4)(x+1)}{x-3} \geq 0} \atop {x\ne 3}} \right. \\\\---[\, -1\, ]+++(3)---[\, 4\, ]+++\\\\x\in [-1,3)\cup [\, 4,+\infty )$