Đáp án:
$9.D\\ 10.D$
Giải thích các bước giải:
$9)\\ P=\left(1+\dfrac{a+\sqrt{a}}{\sqrt{a}+1}\right)\left(1-\dfrac{a-\sqrt{a}}{\sqrt{a}-1}\right)(a \ge 0; a \ne 1)\\ =\left(1+\dfrac{\sqrt{a}(\sqrt{a}+1)}{\sqrt{a}+1}\right)\left(1-\dfrac{\sqrt{a}(\sqrt{a}-1)}{\sqrt{a}-1}\right)\\ =\left(1+\sqrt{a}\right)\left(1-\sqrt{a}\right)\\ =1-a\\ 10)\\ \sqrt{4x^2}=1\\ \Leftrightarrow 2|x|=1\\ \Leftrightarrow |x|=\dfrac{1}{2}\\ \Leftrightarrow x=\pm \dfrac{1}{2}.$
