Hello all,

I am having a hard time understanding how to differentiate summation operators. More specifically, I was given the following solution that I do not understand. Any step by step advice (or a link) would be fantastic....

$\displaystyle $\dfrac{d}{dx}$$\sum\nolimits_{i}p_{i}x_{i}=p_{i}$$ I do not understand why this is equal to p, not the sum of p

Thank you kindly for the help,

Nick