TRả lời ;..............................................
SCSH: ( 100 - 1,2 ) : 2 = 49,4
Tổng: ( 100 + 1,2 ) : 2 = 50,6
Hk tốt,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,
k nhé
3A = 1.2.3+2.3(4-1)+3.4.(5-2)+.+99.100.(101-98)
3A = 1.2.3+2.3.4-1.2.3+3.4.5-2.3.4+.+99.100.101-98.99.100
3A = 99.100.101
SCSH:
( 100 - 1,2 ) : 2 = 49,4
Tổng:
( 100 + 1,2 ) : 2 = 50,6
vậy ............
Đặt A=1.2+3.4+5.6+....+99.100
A=1.(3-1)+3.(5-1)+.....+99(101-1)
A=1.3-1+3.5-3+99.101-99
A=(1.3+3.5+....+99.101)-(1+3+5+...+99)
Đặt B=1.3+3.5+....+99.101
6B=1.3.6+3.5.6+....+99.101.6
6B=1.3.(5+1)+3.5.(7-1)+.....+99.101.(103-97)
6B=1.35+1.3.1+3.5.7-1.3.5+...+99.101.103-97.99.101
6B=1.3.1+99.101.103
B=\(\frac{1.3.1+99.101.103}{6}\)
B=171650
Đặt C=1+3+5+...+99
C=[(99-1):2+1]:2.(99+1)
C=50:2.100
C=25.100
C=2500
Mà A=B-C
A=171650-2500
A=169150
