Trả lời:

\(\sqrt{\dfrac{49}{100}}=\sqrt{\dfrac{7}{10}}\)

\(\sqrt{\dfrac{49}{100}}=\dfrac{7}{10}\)

\(\dfrac{2}{5}+\dfrac{3}{5}x=\left(\dfrac{1}{5}\right)^7\times\left(\dfrac{1}{5}\right)^5\)

\(\Rightarrow\dfrac{2}{5}+\dfrac{3}{5}x=\left(\dfrac{1}{5}\right)^{12}\)

\(\Rightarrow\dfrac{3}{5}x=-0,3999999959\)

\(\Rightarrow x=-0,9999999959\).

     \(\dfrac{6^8.4^3}{9^4.12^6}\)

=   \(\dfrac{2^8.3^8.2^6}{3^8.3^6.2^{12}}\)

= 4/729

n là số j v bạn ?

A=\(\dfrac{1}{3}+\dfrac{2}{3^2}+\dfrac{3}{3^3}+...+\dfrac{100}{3^{100}}\)

⇒3A=\(1+\dfrac{2}{3}+\dfrac{3}{3^2}+...+\dfrac{100}{3^{99}}\)

⇒\(3A-A=\left(1+\dfrac{2}{3}+\dfrac{3}{3^3}+...+\dfrac{100}{3^{99}}\right)-\left(\dfrac{1}{3}+\dfrac{2}{3^2}+\dfrac{3}{3^3}+...+\dfrac{100}{3^{100}}\right)\)

⇒\(2A=1+\left(\dfrac{1}{3}+\dfrac{1}{3^2}+\dfrac{1}{3^3}+...+\dfrac{1}{3^{99}}\right)-\dfrac{100}{3^{100}}\)

⇒\(2A=1+\dfrac{1}{2}-\dfrac{1}{2\cdot3^{99}}-\dfrac{100}{3^{100}}\)

⇒\(A=\dfrac{3}{4}-\dfrac{1}{4\cdot3^{99}}-\dfrac{50}{3^{100}}< \dfrac{3}{4}\)

Vậy......

đk xđ : x - 5 > 0 ⇔ x > 5

Diện tích viên gạch:

`60xx60=3600(cm^2)`

Diện tích căn phòng là:

`3600xx400=1440000(cm^2)=144(m^2)`

D/s....

giúp tui trl ddii ><