\(\frac{1}{\sqrt{1}+\sqrt{2}}+\frac{1}{\sqrt{2}+\sqrt{3}}+.....+\frac{1}{\sqrt{899}+\sqrt{900}}\)

=\(\frac{\sqrt{1}-\sqrt{2}}{1-2}+\frac{\sqrt{2}-\sqrt{3}}{2-3}+....+\frac{\sqrt{899}-\sqrt{900}}{899-900}\)

\(=\frac{\sqrt{1}-\sqrt{2}}{-1}+\frac{\sqrt{2}-\sqrt{3}}{-1}+....+\frac{\sqrt{899}-\sqrt{900}}{-1}\)

\(=\frac{\sqrt{1}-\sqrt{2}+\sqrt{2}-\sqrt{3}+....+\sqrt{899}-\sqrt{900}}{-1}\)

\(=\frac{\sqrt{1}-\sqrt{900}}{-1}\)

\(=\frac{1-30}{-1}=\frac{-29}{-1}=29\)

=

Chiều dài là \(14\frac{3}{5}x2=29\frac{1}{5}\) m

Diện tích là \(14\frac{3}{5}.29\frac{1}{5}=426\frac{8}{25}\)m²

ưn..mk kb òi nha...hihi^^

(1-2m)² - 4m(m-2) >0

1-4m +4m²-4m² +8m >0

4m +1 >0

m > -1/4