Is there a specific trick to solve these kind of math problems?

Question

Hey everyone! I'm kind of stuck on these 8th grade math problems, would anyone mind breaking it down for me? the whole process would be a lifesaver!

1- (1396-1)(1396-2)…(1396-2016)(1396-2017) =

2- What is the product of all even numbers between 300 and -300?

3- 4-9+14-19+24-29+...+94-99 =

Answer 1

Questin number 2 gives a hint;

1) (1396-1)(1396-2)…(1396-2016)(1396-2017) = 0,

Why? because one of the multipliers will be 0 So without any thinking the answer is 0\

3) 3- 4-9+14-19+24-29+...+94-99 =

= -5 -5-... -5 = Now you have to count how many -5's we have, and the answer will be -5 times that number.

2) Think yourself. (is zero an odd or even number?)