1)3a*4b^2+6a^2b+6ba*(-2b)-0.2a*30b=12ab²+6a²b-12ab²-6ab=
=6a²b-6ab=6ab(a-1)
2)7y^2-(3xy-3y^2)+(2xy-10y^2)=7y²-3xy+3y²+2xy-10y²=-xy
при x=1, y=-2
-(1*(-2))=2
3) (c-4)²-3(4-c)³=(-1(4-c))²-3(4-c)³=(-1)²(4-c)²-3(4-c)³=(4-c)²-3(4-c)³=(4-c)²(1-3(4-c))=(4-c)²(1-12+3c)=(4-c)²(3c-11)
4)5x^2+0.5x=0
x(5x+0,5)=0
x=0
5x+0,5=0
5x=-0,5
x=-0,1