1)2m(a-3)+5c(a-3)=(2m+5c)(a-3)
2)(x-y)+x-y=(x-y)+(x-y)=2(x-y)
3)6(m-2)+n(n-2)=(6+n)(m-2)
4)y-xy=y(1-x)
5)9ab+a=a(9b+1)
-1<=сos2x<=1
-4<=4cos2x<=4
-7<=-3+4cos2x<=1
[-7;1]