Question

(2x - 3)² = 81

2 TH

Answer 1

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

\(\Leftrightarrow\left(2x-3\right)^2=\pm\sqrt{81}\)

\(\Leftrightarrow\left(2x-3\right)=\pm9\)

\(\Leftrightarrow\left[\begin{array}{nghiempt}2x-3=9\\2x-3=-9\end{array}\right.\Leftrightarrow\left[\begin{array}{nghiempt}2x=12\\2x=-6\end{array}\right.\)

\(\Leftrightarrow\left[\begin{array}{nghiempt}x=6\\x=-3\end{array}\right.\)

Vậy \(x\in\left\{6;-3\right\}\)

 

Answer 2

(2x- 3)²= 81

(2x- 3)²=9²

2x-3= 9 2x-3= -9

2x = 9+3 2x = (-9)+3

2x = 12 2x = -6

x = 12:2 x = -6:2

x = 6 x = -3

VAY x = 6 va x = -3