Finding conditions for which an inequality holds

[kalish1]

Hello,
I do not know if this is the right place to post this question, but I believe it falls under algebra. Please redirect me if appropriate.

Question:

How can I show that $$P-QR^3<\frac{R^4}{C}$$ for $$C,P,Q,R > 0?$$

Thanks.

 

[magneto1]

That statement is not true in general.
Consider $P=1000$, $Q=2$, $R=3$, $C=10000$, the inequality would be false.