Mẫu số = M = 2830 + 2828 + 2826 + ..... + 282 + 1
= (2830 + 2826 + 2822 + .....+ 282) + (2828 + 2824 + 2820 +.... + 1)
= 282(2828 + 2824 + 2820 + ..... + 1) + (2828 + 2824 + 2820 + ....+ 1)
= (282 + 1)(2828 + 2824 + 2820 + .....+ 1)
= 785(2828 + 2824 + 2820 + .....+ 1) = 785. Tử số
=> \(\frac{28^{28}+28^{24}+28^{20}+....+28^4+1}{28^{30}+28^{28}+28^{26}+....+28^2+1}=\frac{1}{785}\)