Cho \(H\left(x\right)=5x^4+9x-11=0\Leftrightarrow x=\dfrac{-9\pm\sqrt{301}}{10}\)

Ta có: 

\(\dfrac{1}{4}< 1\\ \dfrac{3}{6}< 1\\ \dfrac{5}{8}< 1\\ ...\\ \dfrac{997}{1000}< 1\\ \Rightarrow A=\dfrac{1}{4}\times\dfrac{3}{6}\times\dfrac{5}{8}\times...\times\dfrac{997}{1000}< 1\times1\times1\times...\times1\\ \Rightarrow A< 1< 12900\)

Tính diện tích gì vậy bạn, 1 mặt hay là xung quanh 

\(10a+b=3\left(10a+b\right)+5\Leftrightarrow10a+b=30a+3b\)

\(\Leftrightarrow20a+2b=0\Leftrightarrow10a+b=0\)

\(\overline{ab4}\times3-37=\overline{7ab}\)

\(\left(\overline{ab}\times10+4\right)\times3-37=700+\overline{ab}\)

\(\overline{ab}\times30+12-37=700+\overline{ab}\)

\(\overline{ab}\times30-25-\overline{ab}=700\)

\(\overline{ab}\times30-\overline{ab}=725\)

\(\overline{ab}\times\left(30-1\right)=725\)

\(\overline{ab}\times29=725\)

\(\overline{ab}=\dfrac{725}{29}\)

\(\overline{ab}=25\)

\(\overline{ab4}\) x 3 - 37 = \(\overline{7ab}\)

(\(\overline{ab}\) x 10 + 4) x 3 - 37 = 700 + \(\overline{ab}\)

\(\overline{ab}\) x 30 + 12 - 37 = 700 + \(\overline{ab}\)

\(\overline{ab}\) x 30 + 12 - 37 - \(\overline{ab}\) = 700

\(\overline{ab}\) x (30 - 1) + 12 - 37 = 700

\(\overline{ab}\) x 29 + 12 - 37 = 700

\(\overline{ab}\) x 29 + 12 = 700 + 37

\(\overline{ab}\) x 29 + 12 = 737

\(\overline{ab}\) x 29 = 737 - 12

\(\overline{ab}\) x 29 = 725

\(\overline{ab}\)         = 725 : 29

\(\overline{ab}\)         = 25

Vậy \(\overline{ab}\) = 25

\(\dfrac{a}{4}=\dfrac{b}{5}\\ \Rightarrow\dfrac{a}{b}=\dfrac{4}{5}\\ \Rightarrow\dfrac{b}{a}=\dfrac{5}{4}\\ \Rightarrow\dfrac{4}{a}=\dfrac{5}{b}\)