I know this is a really elementary problem, but I can't seem to figure it out.
How do you factor: $(y^{3}-125)$?
The answer I got is $(y+5)(y^{2}-5y-25)$ but something about the signs just doesn't work.
How should this be factored?
Factor $(y^{3} – 125)$
factoringpolynomials
Best Answer
This is just the difference of cubes.
The way to factor the difference of cubes is: $$(a^{3}-b^{3}) = (a-b)(a^{2}+ab+b^{2})$$.
In this case, your problem is really asking: $(y^{3}-5^{3})$. $y$ is $a$ and 5 is $b$. When you plug it all in, you get $(y-5)(y^{2}+5y+25)$. Your answer is almost right, but the signs are mixed up.