Bài 90: trang 43 sgk Toán 6 tập 2
Tìm x, biết:
| a) \(x.{3 \over 7} = {2 \over 3}\) | d) \({4 \over 7}.x - {2 \over 3} = {1 \over 5}\) |
| b) \(x \div {8 \over {11}} = {{11} \over 3}\) | e) \({2 \over 9} - {7 \over 8}.x = {1 \over 3}\) |
| c) \({2 \over 5} \div x = {{ - 1} \over 4}\) | g) \({4 \over 5} + {5 \over 7} \div x = {1 \over 6}\) |
Bài Làm:
a) \(x.{3 \over 7} = {2 \over 3}\)
\(x=\frac{2}{3} \div \frac{3}{7}\)
\(x=\frac{2}{3} .\frac{7}{3} \)
\(x=\frac{14}{9}\)
b) \(x \div {8 \over {11}} = {{11} \over 3}\)
\(x=\frac{11}{3}.\frac{8}{11}\)
\(x=\frac{8}{3}\)
c) \({2 \over 5} \div x = {{ - 1} \over 4}\)
\(x=\frac{2}{5} \div \frac{-1}{4}\)
\(x=\frac{2}{5} .(-4)\)
\(x=\frac{-8}{5}\)
d) \({4 \over 7}.x - {2 \over 3} = {1 \over 5}\)
\({4 \over 7}.x=\frac{1}{5}+\frac{2}{3}\)
\({4 \over 7}.x=\frac{13}{15}\)
\(x=\frac{13}{15} \div \frac{4}{7}\)
\(x=\frac{91}{60}\)
e) \({2 \over 9} - {7 \over 8}.x = {1 \over 3}\)
\({7 \over 8}.x=\frac{2}{9} -\frac{1}{3}\)
\({7 \over 8}.x=\frac{-1}{9}\)
\(x=\frac{-1}{9} \div \frac{7}{8}\)
\(x=\frac{-8}{63}\)
g) \({4 \over 5} + {5 \over 7} \div x = {1 \over 6}\)
\({5 \over 7} \div x=\frac{1}{6} -\frac{4}{5}\)
\({5 \over 7} \div x=\frac{-19}{30}\)
\(x=\frac{5}{7} \div \frac{-19}{30}\)
\(x=\frac{-150}{133}\)