√x exista daca x≥ 0
daca 5 < √x < 6 ridicam la patrat
5² < √x² < 6²
25 < x < 36
daca x∈ ( 25 ; 36) atunci √x∈( 5 ; 6 )
daca x ∈ N ⇒ x = 26 ;27 ;28 ;29 ;30 ;31 ;32 ;33 ;34 ;35
b. -10 ≤ - √x ≤ - 9 inmultim cu ( -1 ) , se schimba inecuatia !!
9 ≤ √x ≤ 10 ridicam la patrat
9² ≤ √x² ≤ 10²
81 ≤ x ≤ 100
daca x ∈ [81 ; 100 ] atunci √x ∈[ 9 ; 10 ]
