\(=( 1 - 2 - 3 + 4 ) + ( 5 - 6 - 7 + 8 ) + ....+ ( 601 - 602 - 603 + 604 ) = 0 + 0 + .. + 0 = 0 \)
=4+1-2-3+8+5-6-7+...+604+601-602-603
=5-(2+3)+13-(6+7)+...+1205-(602+603)
=0+0+...+0
=0
1-2-3+4+5-6-7+...+601-602-603+604
=-4+4+ -8+8 +....+ -604+604
=0+0 +...+0
=0
1 - 2 - 3 + 4 + 5 - 6 - 7 + ... + 601 - 602 - 603 + 604
= ( 1 - 2 - 3 + 4 0 + ( 5 - 6 - 7 + 8 ) + .... + ( 601 -602 - 603 + 604 )
= 0 + 0 + 0 + ... + 0
= 0
=5+5^2+5^3+....+5^60
=(5+5^2)+(5^3+5^4)+....+(5^59+5^60)
=5(1+5)+53(1+5)+...+559(1+5)
=(5+53+...+559)(5+1)
=(5+53+...+559)6 chia hết cho 6
=> điều phải chứng minh
