Identity of sum $\sum_{a}^{b}x=-\sum_{b}^{a}x$

Question

Does $\sum_{a}^{b}x=-\sum_{b}^{a}x $ is correct?

Answer 1

No, reversed indexes are interpreted as either

• no term in the sum (i.e. $0$) or

• same as in the normal order.

But never opposite of the sum.