Factor:

-5a^(2)b+10ab^(2)-20b+25a^(3)b

id like to see step by step to solving this! !

5b out of -5a^2b+10a^2=20b+25a^3b. 
Put 5b on the outside of the whole equation and divide each number by 5
-5a^2 turns into -a^2+
10ab^2 turns into 2ab(no square)
20b turns into 4b
25a^3b turns into 5a^3
so your equation would be 5b(-a^2+2ab-4+5a^2)

Ithink it is correct but just ask someone else but i am sure it it