Can you tell me what ∑xy means? Like is in the sum of all x times y or what?

Answer 1

the ∑ is the sigma symbol and stands for a summation.
There is probably something like x = ? and y = ? below the symbol and a pair of numbers above it
e.g.
if it says x = 2, y=3 to whatever on top, then it would mean
(2)(3) + (3)(4) + (4)(5) + ....

Answer 2

Thanks so much!!!