I am going through the solution for a problem (1.7 from Goldstein's Classical Mechanics) where it says:

![enter image description here](https://i.stack.imgur.com/rZDLx.jpg)

I don't understand why the right-hand side of the second line only contains 4 terms when there should be 5. The very last term on line 1 has been expanded into 1 term on line 2 using the product rule, but according to the product rule there should be 2 terms.