Đặt A = 1/3×5 + 1/5×7 + 1/7×9 + ... + 1/97×99
2A = 2/3×5 + 2/5×7 + 2/7×9 + ... + 2/97×99
2A = 1/3 - 1/5 + 1/5 - 1/7 + 1/7 - 1/9 + ... + 1/97 - 1/99
2A = 1/3 - 1/99
2A = 32/99
A = 32/99 : 2
A = 32/99 × 1/2 = 16/99
1/5x7 + 1/7x9 + 1/9x11 +………1/97x99
bieu thuc 4/3x5+4/5x7+4/7x9=..........................+4/97x99+4/99x101 có gia trị là bao nhiêu ?
1/1x3 + 1/3x5 + 1/5x7 + .... + 1/97x99
1/1x3 + 1/3x5 + 1/5x7 + 1/7x9
1/3x5 + 1/5x7 + 1/7x9 + ... + 1/2009x2011
1/3x5+1/5x7+1/7x9+........+1/99x101
1/3x5 + 1/5x7 + 1/7x9 +...+ 1/99x101
1/1x3+1/3x5+1/5x7+1/7x9
1/3x5+1/5x7+1/7x9+...+1/999x1001
