giúp em gấp ạ!
1. Cho B= \(\left(\frac{3}{\sqrt{y}-1}+\frac{\sqrt{y}-3}{y-1}\right):\left(\frac{y+2}{y+\sqrt{y}-2}-\frac{\sqrt{y}}{\sqrt{y}+2}\right)\)
a) tìm điều kiện
b) rút gọn
c) tìm y để B=\(\sqrt{y}-1\)
2. Cho B=\(\left(\frac{1}{b-\sqrt{b}}+\frac{1}{\sqrt{b}-1}\right):\frac{\sqrt{b}+1}{b-2\sqrt{b}+1}\)
a) rút gọn
b) tính B biết b=\(3+2\sqrt{2}\)
\(2:Dk:b\ge0;b\ne1\)
\(B=\left(\frac{1}{b-\sqrt{b}}+\frac{\sqrt{b}}{b-\sqrt{b}}\right):\frac{\sqrt{b}+1}{\left(\sqrt{b}-1\right)^2}=\frac{\sqrt{b}+1}{\sqrt{b}\left(\sqrt{b}-1\right)}.\frac{\left(\sqrt{b}-1\right)^2}{\sqrt{b}+1}=\frac{\sqrt{b}-1}{\sqrt{b}};b=3+2\sqrt{2}=2+2\sqrt{2}+1=\left(\sqrt{2}+1\right)^2\Rightarrow B=\frac{\sqrt{2}}{\sqrt{2}+1}\)
