so sánh A = 1/10 + 1/15 + 1/21 + ... +1/66 VÀ B = 1/6 + 1/10 + 1/15 +... +1/55
tính nhanh : A = 1/10+1/15+1/21+........+1/66
1/10+ 1/15 + 1/21 +.........+1/66
Tính nhanh:
a)1/3+1/15+1/35+...1/195
b)6/8+6/56+6/140+...6/416
c)1/10+1/15+1/21+...1/66
Tính nhanh:
\(\frac{1}{10}+\frac{1}{15}+\frac{1}{21}+...+ \frac{1}{66}\)
Tính hợp lý;
\(\frac{1}{10}+\frac{1}{15}+\frac{1}{21}+.....+\frac{1}{66}\)
tính A = 1/15+1/21+1/28+1/36+1/45+1/55+1/66
TÌM X BIẾT :
x/2017-1/10-1/15-1/21-1/28-1/36-1/45-1/55-1/66-1/78-1/91-1/105-1/120=5/8
tính
1/15+1/21+1/28+1/36+1/45+1/55+1/66