Tính tích (3/429 - 1/1.3)(3/429 - 1/3.5)......(3/429 - 1/129.121)(3/429 - 1/121.123)

Tính tích:

\(A=\left(\frac{3}{429}-\frac{1}{1\times3}\right)\times\left(\frac{3}{429}-\frac{1}{3\times5}\right)\times...\times\left(\frac{3}{429}-\frac{1}{119\times121}\right)\times\left(\frac{1}{429}-\frac{2}{121\times123}\right)\)

A=(3/429-1/1.3).(3/429-1/3.5).(3/429-1/5.7)...(3/429-1/121.123)

1) Chứng minh rằng với mọi số nguyên n thì phân số   3n+7 / 4n+9  là phân số tối giản

2) Tính   (5/6 + 19/20 + 41/42 + 71/72 + 109/110 ) - (3/2 +13/12 + 31/30 + 57/56 + 91/90 )

3) tính ( 3/429 -1/1.3 ) (3/429 - 1/3.5 ) ( 3/429 - 1/5.7 ) ( 3/429 - 1/99.101 )

tính A= \(\left(\frac{3}{429}-\frac{1}{1.3}\right).\left(\frac{3}{429}-\frac{1}{3.5}\right)..........\left(\frac{3}{429}-\frac{1}{121.123}\right)\)

Tính B= \(\left(\frac{3}{429}-\frac{1}{1.3}\right)\left(\frac{3}{429}-\frac{1}{3.5}\right)....\left(\frac{3}{429}-\frac{1}{119.121}\right)\left(\frac{3}{429}-\frac{1}{121.123}\right)\)

Tính C= \(\frac{1}{5.6}+\frac{1}{10.9}+\frac{1}{15.12}+...+\frac{1}{3350.2013}\)

159753

852 

1475369

74123

8426

852

Có ý nghĩa gì????

A=(3/429-1/1*3)*(3/429-1/3*5)*...*(3/429-1/121*123)  = ?

 (\(\frac{3}{429}\)-\(\frac{1}{1.3}\)).(\(\frac{3}{429}\)-\(\frac{1}{3.5}\)).......(\(\frac{3}{429}\)-\(\frac{1}{119.121}\)).(\(\frac{3}{429}\)-\(\frac{1}{121.123}\)) Tính tích