Đáp án:
Tham khảo
Giải thích các bước giải:
$(5+2√6)(49-20√6)(\sqrt{5-2√6})$
$=(5+2√6)(7².2².5√6)(\sqrt{5-2√6})$
$=(5+2√6)(5-2√6)(7-5√6)$
$=25-24.(7-5√6)$
$=7-5√6$
$H=\dfrac{\sqrt{x-1-2\sqrt{x-2}} }{\sqrt{x-2}-1 }$
$H=\dfrac{\sqrt{x-2-2\sqrt{x-2}} }{\sqrt{x-2}-1 }$
$H=\dfrac{|\sqrt{x-2}-1| }{\sqrt{x-2}-1 }$
Nếu $\sqrt{x-2}≥1⇔x≥3$
$H=\dfrac{\sqrt{x-2}-1}{\sqrt{x-2}-1 }=1$
Nếu $\sqrt{x-2}<1⇔x<3$
$H=\dfrac{-(\sqrt{x-2}-1)}{\sqrt{x-2}-1 }=-1$
