Question

(2x-3)²  =81

Answer 1

Vì 9^9=81

=>2x-3=9

=>2x=12

=>x=6

Answer 2

(2x - 3)² = 81 

=> (2x - 3)² = 9² = (-9)²

=> \(2x-3\in\left\{9;-9\right\}\)

=> \(2x\in\left\{12;-6\right\}\)

=> \(x\in\left\{6;-3\right\}\)

Vậy \(x\in\left\{6;-3\right\}\)

Answer 3

(2x - 3)² = 81 

=> (2x - 3)² = 9² = (-9)²

=> \(2x-3\in\left\{9;-9\right\}\)

=> \(2x\in\left\{12;-6\right\}\)

=> \(x\in\left\{6;-3\right\}\)