A=1/3+1/6+1/10+1/15+...+1/66
B= 2/15+2/35+2/63+..+2/399
B = 2/15 + 2/35 + 2/63 +...+ 2/399
A=\(\dfrac{2}{15}\)+\(\dfrac{2}{35}\)+\(\dfrac{2}{63}\)+...+\(\dfrac{2}{399}\)
tính hợp lí:
2/15+2/35+2/63+......+2/399
A=\(\frac{2}{15}+\frac{2}{35}+\frac{2}{63}+...+\frac{2}{399}\)
a) A= 4/3.7 + 4/7.11 + 4/11.15 +...+ 4/107.111
b) B= 2/15 + 2/35 +2/63+...+ 2/399
c) C= 1/10 + 1/15 + 1/21+ ...+ 1/120
C=\(\frac{2}{15}\)+\(\frac{2}{35}+\frac{2}{63}+...+\frac{2}{399}\)
cách giải bài : 1^15+1^35+1^63+1^99+...+1^399+1^483. tính b
Ngày 17-3-2018
Bài 1: Tính nhanh:
A= 1/25×27 + 1/27×29 +1/29×31 + ... +1/83×85.
B= 15/90×94 + 15/94×98 +15/98×102 + ... + 15/156×160
C= 2/15 + 2/35 + 2/63 + ... + 2/399