4•(3+у)•(3у-1)=(4-5у)•у как решить?

4•( 3 + y )( 3y - 1 ) = ( 4 - 5y )•y
4( 9y - 3 + 3y^2 - y ) = 4y - 5y^2
4( 3y^2 + 8y - 3 ) = 4y - 5y^2
12y^2 + 32y - 12 - 4y + 5y^2 = 0
17y^2 + 28y - 12 = 0
D = 784 + 816 = 1600 = 40^2
y1 = ( - 28 + 40 ) : 34 = 12/34 = 6/17
y2 = ( - 28 - 40 ) : 34 = - 68 : 34 = - 2
ответ 6/17 ; - 2