Đáp án: $1.B=\dfrac{\sqrt{x}-1}{\sqrt{x}}$ $2.b=5$
Giải thích các bước giải:
1.Ta có :
$B=\left(\dfrac{1}{x-\sqrt{x}}+\dfrac{1}{\sqrt{x}-1}\right):\dfrac{\sqrt{x}+1}{x-2\sqrt{x}+1}$
$\to B=\left(\dfrac{1}{\sqrt{x}\left(\sqrt{x}-1\right)}+\dfrac{\sqrt{x}}{\sqrt{x}\left(\sqrt{x}-1\right)}\right):\dfrac{\sqrt{x}+1}{\left(\sqrt{x}-1\right)^2}$
$\to B=\dfrac{1+\sqrt{x}}{\sqrt{x}\left(\sqrt{x}-1\right)}.\dfrac{\left(\sqrt{x}-1\right)^2}{\sqrt{x}+1}$
$\to B=\dfrac{\sqrt{x}-1}{\sqrt{x}}$
2.Để $y=3x+b$ đi qua $M\left(-1,2\right)$
$\to 2=3\left(-1\right)+b\to b=5$
