bài 1:1.2.3+3.4.5+5.6.7+...+98.99.100
Tính : a, 1.2.3 + 2.3.4 + 3.4.5 + ... + (n - 1).n.(n+1)
b, 1.2.3 + 3.4.5 + 5.6.7 + 98.99.100
549 + X = 1326
X = 1326 - 549
X = 777
X - 636 = 5618
X = 5618 + 636
X = 6254
549 ,1326 ở đâu zậy bạn !!! :/
Bài 1:Tính tổng
A=1.2+3.4+5.6+...+99.100
Bài 2:Tính tổng
A=1.2.3+3.4.5+5.6.7+...+98.99.100
Bài 1:Tính tổng
A=1.2+3.4+5.6+...+99.100
Bài 2:Tính tổng
A=1.2.3+3.4.5+5.6.7+...+98.99.100
Bài 1:Tính tổng
A=1.2+3.4+5.6+...+99.100
Bài 2:Tính tổng
A=1.2.3+3.4.5+5.6.7+...+98.99.100
help me
A=1.2+2.(3.2)+2.(5.3)+...+2.(99.50)
A=2.(3.2+5.3+...+99.50)
A=1.2.3+3.4.5+5.6.7+........+98.99.100
Xin mọi người giúp mình
Đặt A=1.2.3+2.3.4+3.4.5+4.5.6+...+98.99.100
4A=(1.2.3+2.3.4+3.4.5+4.5.6+...+98.99.100)4
4A=1.2.3(4-0)+2.3.4(5-1)+3.4.5(6-2)+4.5.6(7-3)+...+98.99.100(101-97)
4A=1.2.3.4+2.3.4.5-1.2.3.4+3.4.5.6-2.3.4.5+4.5.6.7-3.4.5.6+...+98.99.100.101-97.98.99.100
4A=1.2.3.4-1.2.3.4+2.3.4.5-2.3.4.5+3.4.5.6-3.4.5.6+...+97.98.99.100-97.98.99.100+98.99.100.101
4A=98.99.100.101
=>A=98.99.100.101/4
A = 1.2.3 + 2.3.4 + ... + 98.99.100
4A = 1.2.3.4 + 2.3.4.(5-1) + ... + 98.99.100.(101-97)
4A = 1.2.3.4 + 2.3.4.5 - 1.2.3.4 + ... + 98.99.100.101 - 97.98.99.100
4A = 98.99.100.101
4A = 97990200
A = 24497550
Tính:
A=1.2.3+2.3.4+3.4.5+4.5.6+5.6.7+6.7.8+7.8.9+8.9.10
B=1.3.5+3.5.7+5.7.9+7.9.11+......+95.97.99
C=1.2.3+3.4.5+5.6.7+7.8.9+........+98.99.100
D=1.22+2.32+3.42+4.52+....+99.1002
1/1.2.3 + 1/2.3.4 + 1/3.4.5+...+1/98.99.100 = ?
1/1.2.3 + 1/2.3.4 +....+1/98.99.100
= 1/2 . (3-1/1.2.3 + 4-2/2.3.4 +....+ 100-98/98.99.100)
= 1/2 . (3/1.2.3 -1/1.2.3 + 4/2.3.4 - 2/2.3.4 +.......+ 100/98.99.100 - 98/98.99.100)
= 1/2 . (1/1.2 - 1/2.3 + 1/2.3 - 1/3.4 +......+ 1/98.99 - 1/99.100)
= 1/2 . (1/2 - 1/9900)
= 1/2 . 4949/9900
= 4949/19800
1/1.2.3 + 1/2.3.4 + 1/3.4.5 + ...+1/98.99.100 =?
A=11.2.3+12.3.4+13.4.5+...+198.99.100=11.2−12.3+12.3−13.4+...+198.99−199.100=11.2−199.100=494919800
1.2.3+3.4.5+5.6.7+......+17.18.19