The given mathematical expression is a summation:

$\sum_{i=1}^{4} 2x_i y_i$

Explanation:

• The summation symbol ($\sum$) indicates that we need to sum the expression $2x_i y_i$ over the range of $i$ from 1 to 4.
• This means we compute the values of $2x_i y_i$ for each $i$ from 1 to 4 and sum them together.

Expanded Form:

$2x_1y_1 + 2x_2y_2 + 2x_3y_3 + 2x_4y_4$

If you have specific values for $x_i$ and $y_i$, I can compute the result for you. Let me know if you need further explanation!

Related Questions:

1. What are the properties of summation notation?
2. How do you factor out constants from summations?
3. What are some real-world applications of summations in statistics?
4. How does summation relate to integration in calculus?
5. Can we rewrite this summation using matrix notation?

Tip: When dealing with summations, always check if terms can be factored out to simplify calculations!