a/ \(\dfrac{x-3}{x+5}=\dfrac{5}{7}\)
\(\Leftrightarrow7\left(x-3\right)=5\left(x+5\right)\)
\(\Leftrightarrow7x-21=5x+25\)
\(\Leftrightarrow7x-5x=25+21\)
\(\Leftrightarrow2x=46\)
\(\Leftrightarrow x=23\)
Vậy...
b/ \(\left(2x+3\right)^3=27\)
\(\Leftrightarrow\left(2x+3\right)^3=3^3\)
\(\Leftrightarrow2x+3=3\)
\(\Leftrightarrow x=0\)
Vậy..
1, \(\dfrac{x-3}{x+5}=\dfrac{5}{7}\)
\(\Rightarrow\left(x-3\right).7=\left(x+5\right).5\)
\(\Rightarrow\left(x-3\right).7-\left(x+5\right).5=0\)
\(\Rightarrow7x-21-5x-25=0\)
\(\Rightarrow2x-46=0\)
\(\Rightarrow2x=46\)
\(\Rightarrow x=23\)
Vậy....
2, \(\left(2x+3\right)^3=27\)
\(\Rightarrow\left(2x+3\right)^3=3^3\)
\(\Rightarrow2x+3=3\)
\(\Rightarrow2x=0\)
\(\Rightarrow x=0\)
Vậy..........