數學Arithmetic Sequences既問題 -PLS

NO1-In each of the following Arithmetic Sequences ,find(i) the number of
terms ;
(ii) the first negative term.
(a) 40, 32 , ...,-32
(b)85,79,...,-17

N02-Consider all the multiples of 4 from 100 to 999.
A(i) How many multiples are there?
(ii)Find theSum of these multiples .
(b)Hence find the sum of all the positive there-digit integers which are NOTT divisible by 4.