Section 4.3 - Summation Formulas

The table below gives formulas for several sums that you'll need for the practice questions.

$$\sum_{i=1}^{n} i = 1 + 2 + 3 + . . . + n = \frac{n(n+1)}{2}$$ $$\sum_{i=1}^{n} i^2 = 1 + 4 + 9 + . . . + n^2 = \frac{n(n+1)(2n+1)}{6}$$ $$\sum_{i=1}^{n} i^3 = 1 + 8 + 27 + . . . + n^3 = \left(\frac{n(n+1)}{2}\right)^2$$Next Lesson >