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a)
Số số hạng là : ( 1996 - 1 ) : 1 + 1 = 1996 ( số )
Tổng là : ( 1996 + 1 ) x 1996 : 2 = 1993006
b)c) bạn thực hành nha =))
Số số hạng là :
(1996 - 1) : 1 + 1 = 1996 (số)
Tổng là :
(1996 + 1) x 1996 : 2 = 1993006
Vì 125 125x127 – 127 127x125 = 1001x125x127 – 1001x127x125 = 0
nên : (1+3+5+...+2005)(125 125x127 – 127 127x125) = 0
=(1+...2005)x(125x1001x127-127x1001x125)
=(1+...2005)x0(cả hai vế giống nhau nên trừ đi thì =0)
=0
( 1 + 3 + 5 + 7 +... + 2003 + 2005 ) x ( 125125 x 127 - 127127 x 125 )
= ( 1 + 3 + 5 + 7 + ... + 2003 + 2005 ) x ( 125 x 1001 x 127 - 127 x 1001 x 125 )
= ( 1 + 3 + 5 + 7 + ... + 2003 + 2005 ) x 0
= 0
~ Thiên Mã ~
lllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooolllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllll
1+2-3-4+5+6-7-8+9+..........+2002-2003-2004+2005
=1+(2-3-4+5)+(6-7-8+9)+............+(2002-2003-2004+2005)
=1+0+0+........+0
=1
\(\text{:1+2-3-4+5+6-7-8+9+10-...+2002-2003-2004+2005}\)
\(1+\left(2-3-4+5\right)+\left(6-7-8+9\right)+...+\left(2002-2003-2004+2005\right)\)
= \(1+0+0+....+0\)
= 1
( 1+3+5+7+…+2003+2005) x (125 125 x 127 – 127 127 x 125)
= ( 1+3+5+7+…+2003+2005) x (125 x 1001 x 127 – 127 x 1001x 125)
= ( 1+3+5+7+…+2003+2005) x 0 = 0
1 + 3 + 5 + 7 + ....... + 2003 + 2005
(2005 - 1 ) : 2 : 2 x ( 2005 + 1 )
= 1005006