1/2-1/3-1/15-1/35-1/63-...-1/9999.
-1/3+-1/15+-1/35+-1/63+...+-1/9999
1/3+1/15+1/35+1/63+1/99+……+1/9999
1/3+1/15+1/35+1/63+1/99+……+1/9999
=1/(1×3)+1/(3×5)+1/(5×7)+1/(7×9)+1/(9×11)+……+1/(99×101)
=1/2(1-1/3)+1/2(1/3-1/5)+1/2(1/5-1/7)+1/2(1/7-1/9)+1/2(1/9-1/11)+……+1/2(1/99-1/101)
=1/2(1-1/3+1/3-1/5+1/5-1/7+1/7-1/9+1/9-1/11+……+1/99-1/101)
=1/2(1-1/101)
=1/2×(100/101)
=50/101
1/3+1/15+1/35+1/63+1/99+……+1/9999
=1/(1×3)+1/(3×5)+1/(5×7)+1/(7×9)+1/(9×11)+……+1/(99×101)
=1/2(1-1/3)+1/2(1/3-1/5)+1/2(1/5-1/7)+1/2(1/7-1/9)+1/2(1/9-1/11)+……+1/2(1/99-1/101)
=1/2(1-1/3+1/3-1/5+1/5-1/7+1/7-1/9+1/9-1/11+……+1/99-1/101)
=1/2(1-1/101)
=1/2×(100/101)
=50/101
1/15 + 1/35 + 1/63 + ... + 1/9999 = ?
49/303 chắc chắn lun mình giải rùi tick nha
a/ 1/2 + 5/6 + 11/12 + 19/20
b/ 1/2 + 5/6 + 11/12 + 19/20 + 29/30 + 41/42
c/ (1-1/3) + (1-1/15) + (1-1/35) + (1-1/63)
d/ 1/2 + 5/6 + 11/12 + ... + 9899/9900
e/ 2/3 + 14/15 + 34/35 +62/63
f/ 2/3 + 14/15 + 34/35 + ... + 9998/9999
cái này tính cái gì thế
ko hiểu
1\15+1\35+1\63=1\99+.....1\9999
1/(3x5) + 1/(5x7) + 1/(7x9) + 1/(9x11)+... + 1/(99x101)
(1/3-1/5+1/5-1/7+1/7-1/9+1/9-1/11+...+1/99-1/101) : 2
(1/3 - 1/101) : 2 = 98/303 : 2
49/303
Bạn đưa về dãy tổng
\(\frac{1}{3.5}+\frac{1}{5.7}+.....+\)
Có thể tính nhanh vì đây là dãy đặc biệt
\(\frac{1}{15}+\frac{1}{35}+\frac{1}{63}+\frac{1}{99}+...+\frac{1}{9999}\)
= \(\frac{1}{3.5}+\frac{1}{5.7}+\frac{1}{7.9}+\frac{1}{9.11}+...+\frac{1}{99.101}\)
= \(\frac{1}{3}-\frac{1}{5}+\frac{1}{5}-\frac{1}{7}+\frac{1}{7}-\frac{1}{9}+\frac{1}{9}-\frac{1}{11}+...+\frac{1}{99}-\frac{1}{101}\)
Sau khi lược bỏ các phân số ( phân số cộng với nhau bằng 0 coi như là không cộng)
Ta còn : \(\frac{1}{3}-\frac{1}{101}\)=\(\frac{98}{303}\)
Đáp số: \(\frac{98}{303}\)
1/15 + 1/35 + 1/63 + 1/99 + ....................................+ 1/9999
1/15+1/35+1/63+1/99+...+1/9999=
A = 1/15 + 1/35 + 1/ 63 + 1/99 + ...+ 1/9999
A = 1/(3x5) + 1/(5x7) + 1/(7x9) + 1/(9x11) + ... + 1/(99 x 101)
Ax2 = 2/(3x5) + 2/(5x7) + 2/(7x9) + 2/(9x11) + ... + 2/(99 x 101)
Ax2 = 1/3 – 1/5 + 1/5 – 1/7 + 1/7 – 1/9 + 1/9 – 1/11 + ...+ 1/99 – 1/101
Ax2 = 1/3 – 1/101 = 98/303
A = 98/303 : 2
A = 49/303
1/15 + 1/35 + 1/63 +1/99 + ........ + 1/9999 = ?
1/15+1/35+1/63+1/99+.....1/9999