Video Transcript
Evaluate the sum of negative 25
where 𝑟 takes values from two to six.
As the value we are trying to sum
here is a constant, we might think that the answer is just negative 25. However, the sigma or sum notation
tells us that our series will have five terms, when 𝑟 equals two, three, four,
five, and six. Each of these terms will be equal
to the constant negative 25. This means that we need to add
negative 25, negative 25, negative 25, negative 25, and negative 25. This is the same as multiplying
negative 25 by five, giving us negative 125.
