1)
a) \(\dfrac{2}{5}+\dfrac{3}{10}=\dfrac{4}{10}+\dfrac{3}{10}=\dfrac{7}{10}=0,7\)
b)\(\dfrac{-5}{12}+\dfrac{4}{15}=\dfrac{-25}{60}+\dfrac{16}{60}=\dfrac{-9}{60}=-0,15\)
2)
a) \(2x-\dfrac{3}{2}=\dfrac{5}{2}\)
\(\Leftrightarrow2x=\dfrac{5}{2}+\dfrac{3}{2}\)
\(\Leftrightarrow2x=4\)
\(\Leftrightarrow x=2\)
Vậy x=2
b) \(\left|x+3,8\right|=5,8\)
\(\Leftrightarrow x+3,8=\pm5,8\)
\(\Leftrightarrow\left[{}\begin{matrix}x+3,8=5,8\\x+3,8=-5,8\end{matrix}\right.\)
\(\Leftrightarrow\left[{}\begin{matrix}x=2\\x=-9,6\end{matrix}\right.\)
Vậy x=2 ; x=-9,6
3)
\(2^{255}=2^{3.85}=\left(2^3\right)^{85}=8^{85}\)
\(3^{170}=3^{2.85}=\left(3^2\right)^{85}=9^{85}\)
Vì \(8< 9\)
Nên \(8^{85}< 9^{85}\)
Vậy \(2^{255}< 3^{170}\)
1)
a, \(\dfrac{2}{5}+\dfrac{3}{10}=\dfrac{4}{10}+\dfrac{3}{10}=\dfrac{7}{10}=0,7\)
b)\(\dfrac{-5}{12}+\dfrac{4}{15}=\dfrac{-25}{60}+\dfrac{16}{60}=\dfrac{-9}{60}=-0,15\)
2)
a) \(2x-\dfrac{3}{2}=\dfrac{5}{2}\)
\(\Leftrightarrow2x=\dfrac{5}{2}+\dfrac{3}{2}\)
\(\Leftrightarrow2x=4\)
Vậy x=2
b) \(\left|x+3,8\right|=5,8\)
\(\Leftrightarrow x+3,8=\pm5,8\)
\(\Leftrightarrow\left[{}\begin{matrix}x+3,8=5,8\\x+3,8=-5,8\end{matrix}\right.\)
\(\Leftrightarrow\left[{}\begin{matrix}x=2\\x=-9,6\end{matrix}\right.\)
Vậy x=2 ; x=-9,6
3)
\(2^{255}=2^{3.85}=\left(2^3\right)^{85}=8^{85}\)
\(3^{170}=3^{2.85}=\left(3^2\right)^{85}=9^{85}\)
Vì \(8< 9\)
Nên \(8^{85}< 9^{85}\)
Vậy \(2^{255}< 3^{170}\)
