4(30-2y)-y(30-2y)=0
120-8y-30y+2y²=0
2y²-38y+120=0 l:2
y²-19y+60=0
D=b²-4ac=361-4*1*(60)=361-240=121=11²
x₁=(19-11):2=4
x₂=(19+11):2=15
ответы: 4 ; 15.
4(30-2у)-у(30-2у)=0
4*30-4*2y-y30+y*2y=0
120-8y-30y+2y^2=0
120=8y+30y+2y^2
120=38y+2y^2
120=(38+2+1)*y
120=41y
y=120/41
