Evaluation of Summations

Question

In my textbook, we are given the sum: $ S =\sum_{i=10}^{50} i$.

The solution states that we can write the sum as $ S =\sum_{i=10}^{50} i = (\sum_{i=1}^{50} i) - (\sum_{i=1}^{9} i) $.

My question is how did we get from $\sum_{i=10}^{50} i$ to $ (\sum_{i=1}^{50} i) - (\sum_{i=1}^{9} i) $?

Thanks in advance! Sorry if my formatting is crappy. I'm relatively new to this MathJax thing.

Answer 1

Note that simply we are subtracting $1+...+9$ from $1+...+50$ to obtain $10+...+50$.