We will have the following:
[tex]y^3-y^5=y^3(1-y^2)[/tex]***Explanation***
In order to solve we factor the common values.
We can see that the smallest exponent is 3 and if we subtract y^3 from both values we will have that
[tex]y^3-y^5=y^3\cdot1-y^3\cdot y^2[/tex]So, we can see that they share the same common value, thus:
[tex]y^3(1-y^2)[/tex]We also must remember that:
[tex]y^a\cdot y^b=y^{a+b}[/tex]