S = 1.2.3.4 + 2.3.4.5 + 3.4.5.6+...97.98.99.100

5S = (1.2.3.4+2.3.4.5+3.4.5.6+ ... + 97.98.99.100).5

5S = 1.2.3.4.(5-0) + 2.3.4.5.(6-1)+ 3.4.5.6(7-2)+......+ 97.98.99.100.(101-96)

 5S = (1.2.3.4.5 + 2.3.4.5.6 + 3.4.5.6.7 + ....+ 97.98.99.100.101) - (0.1.2.3.4 + 1.2.3.4.5 + 2.3.4.5.6+.....+96.97.98.99.100)

 5S = 97.98.99.100.101

 S= 97.98.99.100.101/5

 S=1901009880

S=1*2*3*4+2*3*4*5+....+97*98*99*100

5S=1.2.3.4.5+2.3.4.5.5+...+97.98.99.100.5

5S=1.2.3.4.(5-0)+2.3.4.5.(6-1)+...+97.98.99.100.(101-96)

5S=1.2.3.4.5-0.1.2.3.4+2.3.4.5.6-1.2.3.4.5+...+97.98.99.100.101-96.97.98.99.100

5S=(1.2.3.4.5+2.3.4.5.6+...+97.98.99.100.101)-(0.1.2.3.4+1.2.3.4.5+...+96.97.98.99.100)

5S=97.98.99.100.101

S=9505049400:5=1901009880.

S = 1.2.3.4 + 2.3.4.5 + 3.4.5.6+...97.98.99.100

5S = (1.2.3.4+2.3.4.5+3.4.5.6+ ... + 97.98.99.100).5

5S = 1.2.3.4.(5-0) + 2.3.4.5.(6-1)+ 3.4.5.6(7-2)+......+ 97.98.99.100.(101-96)

5S = (1.2.3.4.5 + 2.3.4.5.6 + 3.4.5.6.7 + ....+ 97.98.99.100.101) - (0.1.2.3.4 + 1.2.3.4.5 + 2.3.4.5.6+.....+96.97.98.99.100)

5S = 97.98.99.100.101

S= 97.98.99.100.101/5

S=1901009880 

\(S=\left(1+2+3+...+99\right):5\)

\(S=\frac{\left[\left(99-1\right)+1\right]}{2}.\left(99+1\right):5\)

\(S=\left(\frac{99}{2}.100\right):5\)

\(S=99.50:5\)

\(S=4950:5\)

\(S=990\)

S = ( 1 + 2 + 3 + .......+ 97 + 98 + 99 ) : 5

S x 5 = 1 + 2 + 3 +......+ 98 + 99

S x 5 = ( 99 + 1) + ( 98 + 2) + ( 97+3 )+...........+ ( 51 + 49 ) + 50

S x 5 = 100 + 100 + 100 + 100 +....+ 100 + 50

                 có 49 số 100                         

S x 5 = 100 x 49 + 50

S x 5 = 4900 + 50

S x 5 = 4950

S= 4950 : 5

S = 990

\(\text{S=1 - 2 + 3 - 4 + 5 - 6 + ...+ 97 - 98 + 99 -100.}\)

\(S=\left(1-2\right)+\left(3-4\right)+\left(5-6\right)+......+\left(97-98\right)+\left(99-100\right)\)(50 cặp )

\(S=-1.50\)

\(S=-50\)

Vậy S= -50

Hok tốt !

\(S=1-2+3-4+5-6+...+97-98+99-100\)

\(S=\left(1-2\right)+\left(3-4\right)+\left(5-6\right)+...+\left(97-98\right)+\left(99-100\right)\)

\(S=\left(-1\right)+\left(-1\right)+\left(-1\right)+...+\left(-1\right)+\left(-1\right)\)

\(S=\left(-1\right)\cdot50\)

\(S=-50\)

nhờ các bạn giải ra giùm mình với

[ 1 + 100 ] x 100 = 10100 l i k e nhe

\(S=52\)

S=1-2-3+4+5-6-7+...+97-98-99+100

  =(1-2-3)+4+(5-6-7)+8...+(97-98-99)+100

  =(-4)+4+(-8)+8+...+(-100)+100

  =[(-4)+4]+[(-8)+8]+...+[(-100)+100]

  =0+0+...+0

  =0

\(S=\left(2+4+...+100\right)-\left(1+3+5+...+99\right)\)

\(S=2+4+6+...+100-1-3-5-...-99\)

\(S=\left(2-1\right)+\left(4-3\right)+...+\left(100-99\right)\)

\(S=1+1+1+...+1\)

             50 số hạng

\(S=5.1=5\)

Cái cuối cho mình sửa lại thành S = 50.1 = 50 nha

S= ( 2-1)+ (4-3) + (6-5)+....+ (100-99)

= 1+1+1+...+1 ( 50 chữ số 1)

=50.1 = 50

a)

C = 1 − 2 + 3 − 4 + ... + 97 − 98 + 99 − 100 = 1 − 2 + 3 − 4 + ... + 97 − 98 + 99 − 100 = − 1 + − 1 + ... + − 1 + − 1 = − 1.50 = − 50.

b)

B = 1 − 2 − 3 + 4 + 5 − 6 − 7 + ... + 97 − 98 − 99 + 100 = 1 − 2 + − 3 + 4 + 5 − 6 + ... + 97 − 98 + − 99 + 100 = − 1 + 1 + − 1 + ... + − 1 + 1 = − 1 + 1 + − 1 + 1 + ... + − 1 + 1 − 1 = 0 + 0 + ... + 0 − 1 = − 1.