bonjour

(2x+3)² = 81

(2x+3)² - 81 = 0

(2x+3+9) (2x+3-9) = 0

(2x+12) (2x-6) = 0

soit 2x+12 = 0 => x = -6

soit 2x-6 = 0 => x = 3

√(5x-3) = 8

=> 5x-3 = 8²

5x = 64 + 3

x = 67/5

ex 2

x/2x+1 = 1

donc x = 1 * (2x+1)         produit en croix

x = 2x + 1

x = - 1

2 / (x-2) = 3 / (x-3)

=> 2 (x-3) = 3 (x-2)

je te laisse terminer

:)