Question

So sánh giá trị 2 biểu thức

a, A = 1/2 × 2/3 + 5/10 và B = 7/8 - 1/4 × 3/2

b, C = 2/3 × 4/5 + 8/15 - 1/15 và D = 1/2 × 5/6 + 2/3 × 3/4

Answer 1

a. \(A=\dfrac{1}{2}\cdot\dfrac{2}{3}+\dfrac{5}{10}\) \(B=\dfrac{7}{8}-\dfrac{1}{4}\cdot\dfrac{3}{2}\)

\(=\dfrac{1}{3}+\dfrac{1}{2}\) \(=\dfrac{7}{8}-\dfrac{3}{8}\\ =\dfrac{1}{2}\)

\(\Rightarrow A>B\)

b. \(C=\dfrac{2}{3}\cdot\dfrac{4}{5}+\dfrac{8}{15}-\dfrac{1}{15}\)

\(=\dfrac{8}{15}+\dfrac{7}{15}\\ =\dfrac{15}{15}\\ =1\)

\(D=\dfrac{1}{2}\cdot\dfrac{5}{6}+\dfrac{2}{3}\cdot\dfrac{3}{4}\)

\(=\dfrac{5}{12}+\dfrac{6}{12}\\ =\dfrac{11}{12}\)

\(\Rightarrow C>D\)