x²=400/729=20²/27²=(20/27)²
deci x²=(20/27)²
x²-(20/27)²=0
(x-20/27)(x+20/27)=0
ca un produs sa fie 0, trebuie ca unul dintre factorisa fie 0
x-20/27=0
x=20/27
x+20/27=0
x=-20/27
Deci S= {-20/27; 20/27}
Problema are 2 solutii
se pot verifica ambele
20/27*20/27=400/729
(-20/27) *(-20/27)=400/729
