Решите уравнение (x^2-3x)^2-2 (x^2-3x)-8=0

Пусть ( х^2 - 3х ) = а
а^2 - 2а - 8 = 0
D = 4 + 32 = 36 = 6^2
a1 = ( 2 + 6 ) : 2 = 4
a2 = ( 2 - 6 ) : 2 = - 2
1) x^2 - 3x = 4
X^2 - 3x - 4 = 0
D = 9 + 16 = 25 = 5^2
X1 = ( 3 + 5 ) : 2 = 4
X2 = ( 3 - 5 ) : 2 = - 1
2) x^2 - 3x = - 2
X^2 - 3x + 2 = 0
D = 9 - 8 = 1
X1 = ( 3 + 1 ) : 2 = 2
X2 = ( 3 - 1 ) : 2 = 1
ответ 1 ; 2 ; 4 ; - 1