30(1.8-y)^2+20(y-1.8)(1.8+y)=50y^2+140.4 решить уравнение

30(1.8-y)^2+20(y-1.8)(1.8+y)=50y^2+140.4
30(3.24-3.6y+y²)+20(y²-3.24)=50y²+140.4
97.2-108y+30y²+20y²-64.8=50y²+140.4
50y²-108y+32.4=50y²+140.4
-108y=108
y=-1