Bài 1 :
# 1 - 5 + 9 - 13 + ... + 393 - 397
= ( 1 - 5 ) + ( 9 - 13 ) + ... + ( 393 - 397 )
= ( -4 ) + ( -4 ) + ... + ( -4 )
= ( -4 ) x 197
= -788
# -2 + 4 - 6 + 8 - ... - 238 + 240
= ( -2 + 4 ) + ( -6 + 8 )+ ... + ( -238 + 240 )
= 2 + 2 + ... + 2
= 2 x 60 = 120
Bài 2 :
I DON NOT KNOW😢😢