Question

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

Answer 1

cách giai 

chỉ giùm mình đi

 

Answer 2

A= 1/3 x 5 + 1/5x7 + 1/7x9 + 1/9x11+....+1/99x101

2A= 2/3x5 + 2/5x7 + 2/7x9 + 2/9x11 +....+ 2/99x101

2A= 1/3 - 1/5 + 1/5 - 1/7 + 1/7 - 1/9 + 1/11 + ....+ 1/99 - 1/101

2A= 1/3 - 1/101

A= ( 1/3 - 1/101 ) : 2 = 98/303 : 2 = 49/303