Question

tính nhanh a=1/15+1/35+1/63+1/99+...+1/9999

ai làm nhanh thì tick cho

Answer 1

=1/3*5+1/5*7+1/7*9+...+1/99*101

=1/3-1/5+1/5-1/7+...+1/99-1/101

=1/3-1/101

=98/303

Answer 2

1/15 + 1/35 + 1/63 + 1/99 + ... + 1/9999 

= 1/(3x5) + 1/(5x7) + 1/(7x9) + ... + 1/(99x101)

= (1/3 - 1/5 + 1/5 - 1/7 + 1/7 - 1/9 + ...+ 1/99 - 1/101) : 2

= (1/3 - 1/101) : 2 

= 98/303 : 2

= 49/303

Answer 3

\(a=\frac{1}{15}+\frac{1}{35}+\frac{1}{63}+....+\frac{1}{9999}\)

\(a=\frac{1}{3.5}+\frac{1}{5.7}+\frac{1}{7.9}+....+\frac{1}{99.101}\)

\(a=\frac{1}{2}.\left(\frac{1}{3}-\frac{1}{5}+\frac{1}{5}-....-\frac{1}{101}\right)\)

\(a=\frac{1}{2}.\left(\frac{1}{3}-\frac{1}{101}\right)=\frac{49}{303}\)

Answer 4

trần bảo nam sai rồi sao lại /2