1)
4y²-9(5y-1)²=(2y)²-(3(5y-1))²=(2y-3(5y-1))(2y+3(5y-1))=(2y-15y+3)(2y+15y-3)=
=(3-13y)(17y-3)
2)
9a²-16(4a-3)²=(3a)²-(4(4a-3))²=(3a-4(4a-3)(3a+4(4a-3))=(3a-16a+12)(3a+16a-12)=
=(12-13a)(18a-12)
3)
25(5m+n)²-4n²=(5(5m+n))²-(2n)²+(5(5m+n)-2n)(5(5m+n)+2n)=
=(25m+5n-2n)(25m+5n+2n)=(25m+3n)(25m+7n)