Question

3.(2x+1)³=81

mình ko bít làm

 

Answer 1

\(\Leftrightarrow\left(2x+1\right)^3=27\\ \Leftrightarrow2x+1=3\\ \Leftrightarrow x=1\)

Answer 2

\(3\left(2x+1\right)^3=81\\ \Leftrightarrow\left(2x+1\right)^3=81:3\\ \Leftrightarrow\left(2x+1\right)^3=27\\ \Leftrightarrow\left(2x+1\right)^3=3^3\\ \Leftrightarrow2x+1=3\\ \Leftrightarrow2x=3-1\\ \Leftrightarrow2x=2\\ \Leftrightarrow x=2:2\\ \Leftrightarrow x=1\)

Answer 3

3(2x+1)³=81

↔(2x+1)³=27

↔(2x+1)³=3³

↔2x+1=3

↔2x=2

↔x=1