Разложите на множители

1) - 5a^2-10ab-5b^2

2) (x-y) ^2+3 (x-y)

3) a^5-a^3+a^2-1

4) 25-9m^2+6mn-n^2

1) - 5a^2-10ab-5b^2=-5 (a^2+2ab+b^2) = - 5 (a+b) ^2

2) (x-y) ^2+3 (x-y) = (x-y) (x-y+3)

3) a^5-a^3+a^2-1=a^3 (a^2-1) + (a^2-1) = (a^2-1) (a^3+1) = (a-1) (a+1) (a+1) (a^2-a+1) = (a-1) (a^2-a+1) (a+1) ^2