[tex]a)\\x^{2} -25\geq 0\\x^{2} \geq 25\\x\geq 5\\\\b)\\x^{2} -6x+9\leq 0\\(x-3)^{2} \leq 0\\x-3\leq 0\\x\leq 3\\\\c)\\3x-x^{2} >0\\x(3-x)>0\\\\x>0\\lub\\3-x>0\\3>x\\x<3[/tex]
