1 - 2 - 3 + 4 + 5 - 6 - 7 + 8 + .......... - 119 + 120
= ( 1 - 2 - 3 + 4 ) + ( 5 - 6 - 7 + 8 ) + ............. + ( 117 - 118 - 119 + 120 )
= 0 + 0 + ............... + 0
= 0
1-2-3+4+5-6-7+8+...-119+120
=( 1-2-3+4 ) + ( 5-6-7+8 ) +...+ (117-118-119+120 )
=0 + 0 +...+ 0
=0
1-2-3+4+5-6-7+8+.....-119+120
=>= ( 1 - 2 - 3 + 4 ) + ( 5 - 6 - 7 + 8 ) + ............. + ( 117 - 118 - 119 + 120 )
= 0 + 0 + ............... + 0
= 0
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