Bài 1 tính nhanh
S=3/1.4+3/4.7+3/7.11+3/11.14+3/14.17
M=2/1.2+2/2.3+2/3.4+......+2/15.16
Giúp mk vs nhé
Mk tích cho
tinh
a) \(\frac{4}{3.7}\) + \(\frac{4}{7.11}\)+ \(\frac{4}{11.15}\)+ . . . . + \(\frac{4}{107.111}\)
b) \(\frac{3^2}{8.11}\)+ \(\frac{3^2}{11.14}\)+ \(\frac{3^2}{14.17}\)+ . . . . + \(\frac{3^2}{197.200}\)
tinh nhanh
S=3/1.4+3/4.7+3/7.11+3/11.14+3/14.17
tính nhanh:
a, 5/2 + 5/6 + 5/18 + 5/54+5/162+5/486
b, 2/3+2/6+2/12+2/24+2/48+2/96+2/192
c, 1/3+1/9+1/27+1/81+1/243+1/729
d, 3/2+3/8+3/32+3/128+3/512
e, 1/2.3+1/3.4+1/5.6+1/6.7+1/7.8
g, 4/3.7+4/7.11+4/11.15+4/15.19+4/19.23+4/23.27
h, 2/2.5+2/5.8+2/8.11+2/11.14+2/14.17
i, 4/1.3.5+4/3.5.7+4/5.7.9+4/7.9.11+4/9.11.13+4/11.13.15
k,2/1.2.3+2/2.3.4+2/3.4.5+2/4.5.6+2/5.6.7+2/6.7.8
\(\dfrac{3^2}{8.11}+\dfrac{3^2}{11.14}+\dfrac{3^2}{14.17}+....+\dfrac{3^2}{197.200}\)
Tính nhanh :
\(\frac{3}{1.4}+\frac{3}{4.7}+\frac{3}{7.11}+\frac{3}{11.14}+\frac{3}{14.17}.\)
Lưu ý nếu ai nghĩ là sai đề thì không phải như vậy .
Cho A=2/3.7 + 2/7.11 + 2/11.15 +...+2/n.(n+4) . Hãy so sánh A với 1/6
2/3.7+2/7.11+...2/71.75+2/75.79
2/3.7 - 2/7.9-2/7.11-...-2/24.27-1/27
