Algebra

The domain of the function f(x) = sqrt(5 - 8x + x^2).

$x^2-8x+5=0\\ x\in\{(4-\sqrt{16-5}),(4+\sqrt{16-5})\}\\ x\in\{(4-\sqrt{11}),(4+\sqrt{11})\}\\ f(x)=\sqrt{(x-4+\sqrt{11})(x-4-\sqrt{11})}=0\\ x_0\in \{(4-\sqrt{11}\ ),(4+\sqrt{11})\}$

$D1_{f(x)}=\mathbb R(-inf \le x<[4-\sqrt{11}])\\ D2_{f(x)}=\mathbb R([4+\sqrt{11}] \le x< inf)$

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