Answer: 4xy²(5-y)
Explanation:
To factorize, we must take out common multiples in both parts of the equation. Think of 20xy² and -4xy³ as two completely separate parts. Now, we need to see which parts of the equation are found in both. For instance, 4 can go into both, an x can go into both, and y² can go into both. Now, we simply factor.
Bring the similarities out to the front: 4xy²()
Now, use division to find what would be inside the parenthesis: 5 - y
Now, combine these two parts: 4xy²(5-y)
To check your work, you can simply multiply the outside of the parenthesis by the inside, and you should get the same as what you started with. Hope this helps!