a) 3 1.4 + 3 4.7 + 3 7.10 + ... + 3 40.43 = 1 − 1 4 + 1 4 − 1 7 + ... + 1 40 − 1 43 = 1 − 1 43 = 42 43
b) 4 2.4 + 4 4.6 + 4 6.8 + ... + 4 2016.2018 = 2 2 2.4 + 2 4.6 + ... + 2 2016.2018 = 2 1 2 − 1 4 + 1 4 − 1 6 + ... + 1 2016 − 1 2018 = 2 1 2 − 1 2018 = 1008 1009
bai1:tinh tong S=1.3+3.5+5.7+...+99.101
bai2 :tinh tong S=1.4+4.7+7.10+...+2017.2020
bai 3: tinh tong N=2.4+4.6+6.8+..+100.102
bai 4: tinh tóng=2.6+6.10+10.14+14.18+...+42.46+50.54
bai 5:tinh tongB=2^2+4^2+6^2+...+100^2
bai 6:C=1^2+3^2+...+100^2
bai7: biet 1^2+2^2+3^2+...+10^2=385 tinh tong 2^2+4^2+6^2+...+20^2
bai 8: tinh tong s=1^2+2^2+3^2+...+99^2
Tính:
3/1.4 + 4/4.7 +3/7.10 + ...+ 3/40.43
A=1/2.3+1/3.4+...+1/99.100
B+5/1.4+5/4.7+...+5/100.103
C=4/2.4+4/4.6+4/6.8+....+4/2008.2010
3/1.4+3/4.7+3/7.10+.....+3/40.43
A= 3/1.4 + 3/4.7 + 3/7.10 +...+ 3/40.43
3/1.4+3/4.7+3/7.10+................+3/40.43+3/43.47 = ?
e) \(\dfrac{3}{1.4}\)+\(\dfrac{3}{4.7}\)+\(\dfrac{3}{7.10}\)+...+\(\dfrac{3}{40.43}\)
Bài tập: Tính tổng
a) A = 1.2+2.3+3.4+...+98.99
b) B = 1.3+3.5+5.7+...+99.101
c) S = 1.4+4.7+7.10+...+2017.2020
d) E= 2.4+4.6+6.8+...+98.100
e) S= 1.2.3+2.3.4+3.4.5+...+98.99.100
f) S= 1.2.3.4+2.3.4.5+3.4.5.6+...+19.20.21.22
tính nhanh
3/1.4 + 3/4.7 + 3/7.10 + ...3/40.43
S=3/1.4 +3/4.7 +3/7.10 +...+3/40.43 +3/43.46
