Moving past sequences, we now look at summations. A summation, as the name implies, is the addition of a sequence of numbers.

As discussed earlier, sequences are ordered. Summations, which add up the terms of a sequence are also ordered; however, they use a special notation to create a shorthand description. Example:

`$\sum\limits_{i=1}^{n}i$`

Where *i = 1* is the initial value, *n* is the terminal or “stop” value, and *i* by itself is the description of a single element of the sequence we will sum. . Suppose *n* is not given as a number. In that case, we see an infinite series, which converges to the target value. This technique provides us with a numerical method for approximating the target value (for example, the natural root *e* we saw earlier). Note that we are not always this fortunate with summations.

### Instructions

**1.**

Does the “stop” value in a summation have to be finite?

Set `checkpoint_1`

to `"yes"`

or `"no"`

.

**2.**

Can the initial value be negative?

Set `checkpoint_2`

to `"yes"`

or `"no"`

.