Có: [tex]C=4+\frac{1}{7^6}+\frac{3}{7}+\frac{4}{7^2}+\frac{-441}{7^6}+\frac{27}{7^5}\\=4+\frac{1}{7^6}+\frac{3}{7}+\frac{4}{7^2}-\frac{441}{7^6}+\frac{27}{7^5}\\=4+\frac{1}{7^6}+\frac{3}{7}+\frac{4}{7^2}-\frac{7^2.9}{7^6}+\frac{27}{7^5}\\=4+\frac{1}{7^6}+\frac{3}{7}+\frac{4}{7^2}+\frac{-9}{7^4}+\frac{27}{7^5}[/tex]
[tex]D=\frac{147}{7^3}+4+\frac{35}{7^7}+\frac{4}{7^2}+\frac{27}{7^5}+\frac{-9}{7^9}\\=\frac{7^2.3}{7^3}+4+\frac{5.7}{7^7}+\frac{4}{7^2}+\frac{27}{7^5}+\frac{-9}{7^9}\\=\frac{3}{7}+4+\frac{5}{7^6}+\frac{4}{7^2}+\frac{27}{7^5}+\frac{-9}{7^9}[/tex]

so sánh dành lại cho bạn
