Question

 найти область определения функции
y=3/x^2+9
y=5x-15/x(x-3)
y=√2x+1/√x-3
y=√2x+1/x-3

Answer 1

$y= frac{3}{ x^{2} +9}$ x∈R
$y= frac{5x-15}{x(x-3)}$  x≠0  x≠3
$y = frac{ sqrt{2x+1} }{ sqrt{x-3} }$
$left { {{2x+1 geq 0} atop {x-3 geq>0}} right.$
$left { {{x geq - frac{1}{2} } atop {x>3}} right.$
⇒ x>3
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$y= frac{ sqrt{2x+1} }{x-3}$
$left { {{x geq - frac{1}{2} } atop {x neq 3}} right.$
x∈[$- frac{1}{2} ;3) (3; infty)$