Question

determine os valores de a para que a equação x^2 -2x - log a = 0

Answer 1

$x^2-2x-log\ a =0\\\\Para \ ter \ ra \’{\i} zes \reais\ \Delta\geq 0$

$\\a=1\ \ \ \ b=-2\ \ \ \ c=-log\ a\\ \\\Delta\geq 0\\ \\b^2-4ac\geq0\\ \\(-2)^2-4\cdot1\cdot(-log\ a)\geq0\\ \\4+4\cdt\ log\ a\geq0\\ \\4\cdt\ log\ a\geq-4\\ \\ log\ a\geq\frac{-4}{4}\\ \\ log\ a\geq-1\\ \\ a\geq10^{-1}\\ \\ a\geq\frac{1}{10}$