1)4y²-(y-c)²=(2y-y+c)(2y+y-c)=(y+c)(3y-c)
2)(a²+2ab+b²)-c²=(a+b)²-c²=(a+b-c)(a+b+c)
3)1-a²-2ab-b²=1-(a²+2ab+b²)=1-(a+b)²=(1-a-b)(1+a+b)
4)a²-b²+a+b=(a-b)(a=b)+(a+b)=(a+b)(a-b+1)
5)x-y-x²+y²=(x-y)-(x²-y²)=(x-y)-(x-y)(x+y)=(x-y)(1-x-y)
6)m^5-m^3+m²-1=m³(m²-1)+(m²-1)=(m²-1)(m³+1)=
=(m-1)(m+1)(m+1)(m²-m+1)=(m+1)²(m-1)(m²-m+1)