1)64+(3с-1)^3 2)a^6 - 25a^2 +10a-1 3)25m^2+30mn+9n^2 4)y^2-10y+25-4m^2 ...

$64+(3c-1)^3=4^3+(3c-1)^3=(4+3c-1)(16+12c-4+9c^2-6c+1)=(3c+3)(9c^2+6c+13)=3(c+1)(9c^2+6c+13)$

$a^6-25a^2+10a-1=a^6-(25a^2-10a+1)=(a^3)^2-(5a-1)^2=(a^3+5a-1)(a^3-5a+1)$

$25m^2+30mn+9n^2=(5m+3n)^2$

$y^2-10y+25-4m^2=(y^2-10y+25)-4m^2=(y-5)^2-(m)^2=(y-5+m)(y-5-m)$

$-9x^{3m}y^n+12x^{5m}y^{3n}-21x^{6m}y^{2n}=-3x^{3m}y^n(3-4x^{2m}y^{2n}+7x^{3m}y^n)$