Question 482003
Any time you factor a polynomial, your first step is to factor out the GCF (Greatest Common Factor).  In your case, both terms are divisible by {{{3y^3}}}, so we factor that out first (and divide both terms by the GCF inside the parentheses): {{{3y^3(y^2-25)}}}.  Now, look inside the parentheses.  That's a difference of two squares, and can be factored...the rule is {{{a^2-b^2=(a+b)(a-b)}}}, so since {{{y^2-25=y^2-5^2}}}, it factors to {{{(y+5)(y-5)}}}.  Don't forget that GCF you factored out; your final answer is {{{3y^3(y+5)(y-5)}}}