1 + 3 - 5 - 7 + 9 + 11 - ... - 397 - 399
= 1 + ( 3 - 5 - 7 + 9 ) + ... + (395 - 397 - 399 + 401 ) - 401
= 1 + 0 + ... + 0 - 401
= 1 - 401
= -400.
1+3-5-7+9+11-...-397-399
=1+(3-5-7+9)+...+ (395.397.399+401)-401
=1+0+.. +0-401
=1-401
=-401
1+3-5-7+9+11-...-397-399
=1+(3-5-7+9)+...+ (395.397.399+401)-401
=1+0+.. +0-401
=1-401
=-401