Question

tìm x

(2.x+1)⁴=81

Answer 1

\(\left(2x+1\right)^4=81\)

\(\left(2x+1\right)^4=3^4\)

\(\left(2x+1\right)=3\)

\(2x=2\)

\(\Rightarrow x=2\)

Answer 2

\(\left(2x+1\right)^4=81=3^4=\left(-3\right)^4\)

\(\Rightarrow\hept{\begin{cases}2x+1=3\\2x+1=-3\end{cases}\Rightarrow\hept{\begin{cases}2x=2\\2x=-4\end{cases}\Rightarrow}\hept{\begin{cases}x=1\\x=-2\end{cases}}}\)

Answer 3

(2.x+1)^4=3^4

suy ra 2.x+1=3

             2.x=2

                x=1