`sqrt(6x - x^2) sin2x = 0(x in [0 ; 6])`

`+) sqrt(6x - x^2) = 0 <=> x in {0 ; 6}`

`+) sin2x = 0 <=> 2x = kpi (k in ZZ)`

Mà `x in [0 ; 6] => 2x in [0 ; 12] => kpi in [0 ; 12] => k in [0 ; 12/(pi)]`

Mà `k in ZZ => k in {0 ; 1 ; 2 ; 3}`

`=> 2x in {0 ; pi ; 2pi ; 3pi} => x in {0 ; (pi)/2 ; pi ; 3/2 pi}`

Vậy pt có `5` nghiệm : `S = {0 ; 6 ; (pi)/2 ; pi ; 3/2 pi}`