Question

1.tính giá trị biểu thức sau một cách hợp lí nếu có

a)\(\frac{1}{3}.\frac{4}{5}+\frac{1}{3}.\frac{6}{5}-\frac{5}{3}\)

b)\(\frac{4}{19}.\frac{-3}{7}+\frac{-3}{7}.\frac{15}{19}+\frac{5}{7}\)

c)\(\frac{6}{7}.\frac{10}{9}+\frac{1}{7}.\frac{10}{9}-\frac{8}{9}\)

Answer 1

a. \(\frac{1}{3}.\frac{4}{5}+\frac{1}{3}.\frac{6}{5}-\)

\(=\frac{1}{3}(\frac{4}{5}+\frac{6}{5})-\frac{5}{3}\)

\(=\frac{1}{3}.2-\frac{5}{3}\)

\(=\frac{2}{3}-\frac{5}{3}\)

\(=-\frac{1}{1}\)

Answer 2

c. \(\frac{6}{7}.\frac{10}{9}+\frac{1}{7}.\frac{10}{9}-\frac{8}{9}\)

\(=\frac{10}{9}\left(\frac{6}{7}+\frac{1}{7}\right)-\frac{8}{9}\)

\(=\frac{10}{9}.1-\frac{9}{8}\)

\(=\frac{10}{9}-\frac{9}{8}\)

\(=-\frac{1}{72}\)

Answer 3

\(b\).\(\frac{4}{19}.\frac{-3}{7}+\frac{-3}{7}.\frac{15}{19}+\frac{5}{7}\)

\(=\frac{-3}{7}\left(\frac{4}{19}+\frac{15}{19}\right)+\frac{5}{7}\)

\(=\frac{-3}{7}+\frac{5}{7}\)

\(=\frac{2}{7}\)

Answer 4

c)\(\frac{6}{7}.\frac{10}{9}+\frac{1}{7}.\frac{10}{9}-\frac{8}{9}\)

\(=\frac{10}{9}\left(\frac{6}{7}+\frac{1}{7}\right)-\frac{8}{9}\)

\(=\frac{10}{9}-\frac{8}{9}\)

\(=\frac{2}{9}\)