1) 4c^2-8c-c+4=4c^2-9c+4
2)(c-4)^2=c^2-8c+16
3)3(y-1)+6y=3y-3+6y=9y-3
4)(y-1)^2=y^2-2y+1
4с(с-2)-(с-4)^2=4c^2-8c-(c^2-8c+16)=4c^2-8c-c^2+8c-16=3c^2-16 (^2-в квадрате)
3(y-1)^2+6y =3(y^2-2y+1)+6y=3y^2-6y+3+6y=3y^2+3=3(y^2+1)
