Originally Posted by

**craig** With these types of equalities you have a couple of chouces.

As you said you cannot multiply both sides by$\displaystyle (x+1)^3$, however you *can* multiply both by$\displaystyle (x+1)^6$, as you know this is a positive number.

You can also make both sides into fractions and add or subtract to rearrange.

For example,$\displaystyle \frac {5} {(x+1)^3} <\frac{N(x+1)^3}{(x+1)^3}$, leading to $\displaystyle \frac {5} {(x+1)^3} - \frac{N(x+1)^3}{(x+1)^3}<0$

Can you solve this from here?