1: \(B=\dfrac{1}{7}-\dfrac{1}{9}=\dfrac{2}{63}>\dfrac{1}{7\cdot9}=A\)

2: \(A=\dfrac{15}{301}< \dfrac{15}{300}=\dfrac{1}{20}=\dfrac{25}{500}< \dfrac{25}{499}\)

\(\Rightarrow A=\frac{5.2.3}{3.3.5.5}=\frac{1.2.1}{1.3.1.5}=\frac{2}{15}\)

     \(B=\frac{3.3.2.2-3.3.2}{2.2.2.3.3+7.3.3}=\frac{1.1.1.1-1.1.2}{2.1.1.1.1+7.1.1}=\frac{-1}{9}\)

=> A > B

Ai thấy đúng k nha

\(A=\frac{5.6}{9.25}=\frac{1.2}{3.5}=\frac{2}{15}.\)

\(B=\frac{18.4-18}{8.9+7.9}=\frac{18\left(4-1\right)}{9\left(8+7\right)}=\frac{18.3}{9.15}=\frac{2.1}{15}=\frac{2}{15}.\)

\(\Rightarrow A=B.\)

A).Bạn lấy 15 : 301 = 0,049

B).Bạn lấy 25 : 499 = 0,050

Vậy là \(\frac{15}{301}\) <  \(\frac{25}{499}\)

\(\frac{15}{301}< \frac{25}{499}\)( dựa vào tích chéo)

\(\Rightarrow A< B\)

Ta quy đồng tử số. Ta có tử số chung là 75:

\(\frac{15}{301}=\frac{15.5}{301.5}=\frac{75}{1505}\)

\\(\frac{25}{499}=\frac{25.3}{499.3}=\frac{75}{1497}\)

Do  \(\frac{75}{1505}< \frac{75}{1497}\)

\(\Rightarrow\frac{15}{301}< \frac{25}{499}\)

\(\Leftrightarrow A< B\)

\(A=\frac{1}{7\cdot9}\)

\(B=\frac{1}{7}-\frac{1}{9}\)

\(2A=\frac{1}{7}-\frac{1}{9}\)

\(\Rightarrow A< B\)

2A = 2 / 7.9

2A = 1/7 - 1/9

=> A < B

A - B = 1/7.9 -1/7 +1/9 =1/9(1/7 -1) -1/7 =1/9 . (-6/7) -1/7 = - (6/ 9.7 +1/7) <0 

nên A<B 

A =  15/301 <  B = 25/499

a) Ta có:
\(\frac{15}{301}>\frac{15}{300}=\frac{1}{20}\)

\(\frac{25}{499}< \frac{25}{500}=\frac{1}{20}\)

Vì \(\frac{1}{20}=\frac{1}{20}\) nên \(\frac{15}{301}>\frac{1}{20}>\frac{25}{499}\) hay \(\frac{15}{301}=\frac{25}{499}\)

Vậy \(\frac{15}{301}>\frac{25}{499}\)

a)Ta có:\(\frac{15}{301}\)<\(\frac{15}{300}\)=\(\frac{1}{20}\)=\(\frac{25}{500}\)<\(\frac{25}{499}\)

Vì \(\frac{15}{301}\)<\(\frac{25}{500}\)<\(\frac{25}{499}\)

\(\Rightarrow\)\(\frac{15}{301}< \frac{25}{499}\)(đpcm)

Còn câu b  thì sao.