Define $$S=\sum _{r=1}^n a_r$$
How to prove the following inequality: $$\prod _{r=1}^n (1+a_r)\leq \sum _{r=0}^n \frac{S^r}{r!}$$
Define $$S=\sum _{r=1}^n a_r$$
How to prove the following inequality: $$\prod _{r=1}^n (1+a_r)\leq \sum _{r=0}^n \frac{S^r}{r!}$$