Question

Giải câu này giúp em với 🤔

Answer 1

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

\(\Rightarrow\left[{}\begin{matrix}2x+1=9\\2x+1=-9\end{matrix}\right.\)

\(\Rightarrow\left[{}\begin{matrix}2x=8\\2x=-10\end{matrix}\right.\)\(\Rightarrow\left[{}\begin{matrix}x=4\\x=-5\end{matrix}\right.\)

Answer 2

(2x + 1)² = 81

<=> (2x + 1)² - 9² = 0

<=> (2x + 1 - 9)(2x + 1 + 9) = 0

<=> (2x - 8)(2x + 10) = 0

<=> \(\left[{}\begin{matrix}2x-8=0\\2x+10=0\end{matrix}\right.\)

<=> \(\left[{}\begin{matrix}x=4\\x=-5\end{matrix}\right.\)