250+120=370грамм общая масса
370гр.-100\%
120гр-?\%
120*100:370=32,4\% массовая доля соли
(-0.15 - 7)(-0.15+4)-(-0.15+3)(-0.15-10) =
1) -0.15-7=-7.15
2) -0.15+4=3.85
3)-7.15*3.85=27.5275
4)-0.15+3=2.85
5)-0.15-10=-10.15
6)2.85*(-10.15)=-28.9275
7)27.5275-(-28.9275)=56.455
S=0.5*absinα=0.5*2*3*sin60=3*√2/3=√2
1)y/(2+3y)-5y)/(3y-2)=(3y²-2y-10y-15y²)/(2+3y)(3y-2)=
=(-12y²-12y)/(2+3y)(3y-2)=-12y(y+1)/(2+3y)(3y-2)
2)-12y(y+1)/(2+3y)(3y-2) * (3y-2)²/4y²(y+1)=-3(3y-2)/y(2+3y)=
=3(2-3y)/y(2+3y)