Question

f(x)=корень -x^2+3x+4/x .Найти область определения

Answer 1

$f(x)=\sqrt{\frac{-x^2+3x+4}{x}}\\\\OOF:\; \; \frac{-x^2+3x+4}{x}\geq 0\; \; ,\; \; \; \frac{-(x+1)(x-4)}{x}\geq 0\; \; ,\; \; \frac{(x+1)(x-4)}{x}\leq 0\; ,\\\\znaki:\; \; ---[-1\; ]+++(0)---[\; 4\; ]+++\\\\x\in D(y)=(-\infty ,-1\, ]\cup (0,4\; ]$

$P.S.\; \; \; \; f(x)=\frac{\sqrt{-x^2+3x+4}}{x}\\\\OOF:\; \; \left \{ {{-x^2+3x+4\geq 0} \atop {x\ne 0\qquad \quad }} \right. \; \; \left \{ {{-(x+1)(x-4)\geq 0} \atop {x\ne 0\qquad \quad }} \right.\; \; \left \{ {{(x+1)(x-4)\leq 0} \atop {x\ne 0\qquad \quad }} \right.\; \; \left \{ {{x\in [-1\, ;\, 4\; ]} \atop {x\ne 0\qquad }} \right. \\\\x\in D(y)=[-1\, ;\, 0)\cup (0\, ;\, 4\; ]$