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trantien.hocmai

$$y=\sqrt{x-1}+\sqrt{5-x}-\sqrt{(x-1)(5-x)}$ \\
\text{đk }1 \le x \le 5 \\
\text{đặt t=}\sqrt{x-1}+\sqrt{5-x} \text{ }t \in [2;2\sqrt{2}] \\
\rightarrow t^2=4+2\sqrt{(x-1)(5-x)} \rightarrow \sqrt{(x-1)(5-x)}=\dfrac{t^2-4}{2} \\
y=t-\dfrac{t^2-4}{2} \\$$
$\text{khảo sát hàm số} f(t)=t-\frac{t^2-4}{2} \text{ }t \in [2;2\sqrt{2}]$
 
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