What does $\sum^n_{r=1} r^2$ mean?

What does \sum^n_{r=1} r^2 mean?

• We start our r ‘counter’ at 1
• Each time, we increase r by 1 until we reach n.
• We include r=n
• For each value of r, we calculate r^2
• Finally, we add all those r^2 values together.

That’s what the \sum symbol means!

Write \frac12+\frac13+\frac14+\frac15+\frac16 using sigma notation

\sum^5_{r=1} \frac{1}{r+1}

Write \frac12+\frac14+\frac18+\frac1{16}+\frac1{32} using sigma notation

\sum^5_{r=1} \frac{1}{2^r}