Ta có:+) \(A=\frac{2^{19}-3}{2^{20}-3}\)
\(2A=\frac{2^{20}-6}{2^{20}-3}=\frac{\left(2^{20}-3\right)-3}{2^{20}-3}\)
\(2A=1-\frac{3}{2^{20}-3}\)
+)\(B=\frac{2^{20}-3}{2^{21}-3}\)
\(2B=\frac{2^{21}-6}{2^{21}-3}=\frac{\left(2^{21}-3\right)-3}{2^{21}-3}\)
\(2B=1-\frac{3}{2^{21}-3}\)
Vì \(2^{20}-3< 2^{21}-3\)nên \(1-\frac{3}{2^{20}-3}< 1-\frac{3}{2^{21}-3}\)
Hok tốt nha^^