Confusing symbols

Question

I saw these symbols in the text book for a subject i'm taking next semester, and I am just curious about what they mean. What is the question asking me?

Answer 1

The "sum" notation $\sum$ means add up the things indexed by some index. An easy example may be

$$ \sum_{i=1}^{10}i=1+2+3+4+5+6+7+8+9+10 $$

you could read this as "sum all the i's from $1$ to $10$".

$$ \sum_{j=-2}^{2}j^2=(-2)^2+(-1)^2+0^2+1^2+2^2 $$

The starting index can be any integer and you sum upto the number above the summation sign. It sometimes can be $\infty$ symbol up there, this means you sum for all the numbers.

The "product" notation works similarly

$$ \prod_{i=1}^{5}=1\cdot 2\cdot 3\cdot 4\cdot5 $$

or

$$ \prod_{j=1}^{3}(j+10)=(1+10)\cdot(2+10)\cdot(3+10) $$

I don't know "what the question is asking" since there is no question in your post.

Hope this helped

Answer 2

See Summation for $\Sigma$.

It "asks" you to compute :

$\dfrac {2}{6.2−7}+\dfrac {2}{6.3−7}+ \ldots +\dfrac{2}{6.6−7}$.

The same with product instead of sum in the formula with the Products of sequences $\Pi$ :

$[(z+2.5)^5-5-1] \times [(z+2.6)^6-6-1] \times \ldots \times [(z+2.8)^8-8-1].$