Nhà nghèo quá ko có tiền mua bông hút, lấy "nùi giẻ" lau là được rồi ! =)) 

\(=\sqrt{3+2+2.\sqrt{3}.\sqrt{2}}\)

\(=\sqrt{3+2.\sqrt{3}.\sqrt{2}+2}\)

\(=\sqrt{\left(\sqrt{3}+\sqrt{2}\right)^2}\)

\(=\sqrt{3}+\sqrt{2}\)

(1+\(\sqrt{5}\))\(^2\)

\(\frac{\sqrt{x^2y^2}}{xy}+\frac{\sqrt{\left(x-y\right)^2x^2}}{x\left(x-y\right)}-\frac{\sqrt{\left(x-y\right)y^2}}{y\left(x-y\right)}\)

\(=\sqrt{\frac{x^2y^2}{x^2y^2}}+\sqrt{\frac{\left(x-y\right)^2x^2}{x^2\left(x-y\right)^2}}-\sqrt{\frac{\left(x-y\right)y^2}{y^2\left(x-y\right)^2}}\)

\(=1+1-\frac{1}{\sqrt{x-y}}\)

\(=2-\frac{1}{\sqrt{x-y}}\)

x-y<0 thì sao ạ

\(\sqrt{5+2\sqrt{5}}\)

\(=\sqrt{5+2\sqrt{5}+1-1}\)

\(=\sqrt{\left(\sqrt{5}+1\right)^2-1}\)

\(=\sqrt{5}+1-1\)

\(=\sqrt{5}\)

Chieu dai 11 m

Chieu rong 7 m

chiều dài là    : 11 m

chiều rộng là :  7 m

Đặt \(\hept{\begin{cases}\sqrt{2\left(x^2-4x-5\right)}=a\\\sqrt{x+4}=b\end{cases}}\)

\(\Rightarrow2x^2-5x+2=4\sqrt{2\left(x^3-21x-20\right)}\)

\(\Leftrightarrow2\left(x^2-4x-5\right)+3\left(x+4\right)=4\sqrt{2\left(x^2-4x-5\right)\left(x+4\right)}\)

\(\Leftrightarrow a^2+3b^2=4ab\)

\(\Leftrightarrow\left(a-b\right)\left(a-3b\right)=0\)

E cảm ơn