Answer:
2019?
Explanation:
1-2-3+4+5-6-7+8+9-10-11+12....+1000+1001-1002
if we take all the positives on one side, :-
1+(4+5)+(8+9)+(12+13)+(16+17)...(1000+1001)
= 1+9+17+25+33....+ 2001 which is an AP where the common diff is +8..
so n = 251 ( which is total terms)
now the sum of all the terms = 251/2 × (2001+1) = 251251
now after applying the same process to the negative terms, we get the sum to be = -249232
after adding the sums of the 2 AP's we get 2019
P.S : I'm Not sure about the answer cause i Did it by hand so wait for another ans or use a calculator
all the best :)
this was a good question... do you mind telling the source?