#Jelly, 5 3 bytes
Jelly, 5 3 bytes
Thanks to @Sp3000 for saving two bytes!
Code, uses quite the same algorithm as @xnor's great answer:
SfḤ
Explanation:
S # Sum of the argument list
Ḥ # Double the list
f # Filter, remove everything that isn't equal to the sum of the list
This gives [] as falsy, and anything else as truthy.