Kiểm tra bài : Nhân, chia số hữu tỉ
Thực hiện phép tính :
(1) \(-\frac{3}{2}.\frac{7}{10}=\frac{-3.7}{2.10}=\frac{-21}{20}\)
(2) \(\frac{-5}{3}.\frac{6}{11}=\frac{-5.6}{3.11}=\frac{-30}{33}\)
(3) \(2\frac{1}{3}.\left(-1\frac{2}{3}\right)=\frac{7}{3}.\left(-\frac{5}{3}\right)=\frac{7.\left(-5\right)}{3.3}=-\frac{35}{9}\)
(4) \(\frac{9}{10}:\left(-\frac{15}{11}\right)=\frac{9}{10}.\left(\frac{-11}{15}\right)=\frac{9.\left(-11\right)}{10.15}=-\frac{99}{150}=-\frac{33}{50}\)
(5) \(\left(-1\right):\frac{3}{8}=\frac{\left(-1\right).8}{3}=-\frac{8}{3}\)
(6) \(\frac{1}{2}.\left(-\frac{5}{4}\right).\frac{8}{7}=\frac{1.\left(-5\right)}{2.4}.\frac{8}{7}=-\frac{5}{8}.\frac{8}{7}=-\frac{5.8}{8.7}=-\frac{5}{7}\)
(7) \(\frac{-9}{2}.\frac{2}{18}.\frac{1}{7}=\left(-\frac{9}{2}.\frac{2}{18}\right).\frac{1}{7}=\left(-\frac{9.2}{2.18}\right).\frac{1}{7}=-\frac{18}{36}.\frac{1}{7}=-\frac{18.1}{36.7}=-\frac{1}{14}\)
(8) \(\left(\frac{9}{2}-\frac{1}{3}\right).\frac{6}{17}=\left(\frac{27}{6}-\frac{2}{6}\right).\frac{6}{17}=\frac{27-2}{6}.\frac{6}{17}=\frac{25}{6}.\frac{6}{17}=\frac{25.6}{6.17}=\frac{25}{17}\)
(9) \(\left(-\frac{12}{13}:\frac{36}{39}\right).\frac{3}{5}=\left(-\frac{12}{13}.\frac{39}{36}\right).\frac{3}{5}=\left(\frac{-12.39}{13.36}\right).\frac{3}{5}=-\frac{1.3}{5}=-\frac{3}{5}\)
(10) \(\left(-\frac{3}{7}+\frac{7}{9}\right):\frac{4}{7}+\left(-\frac{4}{7}+\frac{2}{9}\right):\frac{4}{7}=\left(\left(-\frac{3}{7}+\frac{7}{9}\right)+\left(-\frac{4}{7}+\frac{2}{9}\right)\right):\frac{4}{7}\)
\(=\left(\left(-\frac{27}{63}+\frac{49}{63}\right)+\left(-\frac{36}{63}+\frac{14}{63}\right)\right):\frac{4}{7}=\left(\left(-\frac{27+49}{63}\right)+\left(\frac{-36+14}{63}\right)\right):\frac{4}{7}\)
\(=\left(\left(\frac{22}{63}\right)+\left(-\frac{22}{63}\right)\right):\frac{4}{7}\)
\(=\frac{22+\left(-22\right)}{63}:\frac{4}{7}=\frac{0}{63}:\frac{4}{7}=0\)
Mình đăng các bài toán này lên thứ nhất là để kiểm tra năng lực thứ hai các bạn có thể xem đây và rút ra lời giải cho các bài khác và nếu mình sai chỗ nào các bạn chỉ mình sẽ chỉnh
Bài 1 : Tính :
a, \(-\frac{8}{3}.\frac{6}{13}.\frac{7}{13}.\frac{-3}{8}+1\frac{3}{8}\)
\(=\left(-\frac{8}{3}.-\frac{3}{8}\right).\left(\frac{6}{13}.\frac{7}{13}\right)+1\frac{3}{8}\)
\(=1.\frac{42}{169}+1\frac{3}{8}\)
\(=\frac{2195}{1352}\)
b) \(75\%-\left(\frac{5}{2}+\frac{5}{3}\right)+\left(-\frac{1}{2}\right)^2\)
\(=\frac{3}{4}-\frac{25}{6}+\frac{1}{4}\)
\(=\frac{3}{4}+\frac{1}{4}-\frac{25}{6}\)
\(=1-\frac{25}{6}\)
\(=-\frac{19}{6}\)
~Hok tốt~
Bài 2 :
a)\(\frac{3}{5}.x-\frac{2}{3}=\frac{1}{2}\) b) \(\left(\frac{1}{2}-x\right).\frac{2}{3}=\frac{1}{8}\)
\(\frac{3}{5}.x=\frac{1}{2}+\frac{2}{3}\) \(\frac{1}{2}-x=\frac{1}{8}:\frac{2}{3}\)
\(\frac{3}{5}.x=\frac{7}{6}\) \(\frac{1}{2}-x=\frac{3}{16}\)
\(x=\frac{7}{6}:\frac{3}{5}\) \(x=\frac{1}{2}-\frac{3}{16}\)
\(x=\frac{35}{18}\) \(x=\frac{5}{16}\)
c) \(\left|2x-\frac{3}{7}\right|-\frac{1}{2}=\frac{3}{4}\)
\(\left|2x-\frac{3}{7}\right|=\frac{3}{4}+\frac{1}{2}\)
\(\left|2x-\frac{3}{7}\right|=\frac{5}{4}\)
\(\Rightarrow2x-\frac{3}{7}\in\left\{\frac{5}{4};-\frac{5}{4}\right\}\)
\(TH1:2x-\frac{3}{7}=\frac{5}{4}\) \(TH2:2x-\frac{3}{7}=-\frac{5}{4}\)
\(\Rightarrow2x=\frac{5}{4}+\frac{3}{7}\) \(\Rightarrow2x=-\frac{5}{4}+\frac{3}{7}\)
\(2x=\frac{47}{28}\) \(2x=-\frac{23}{28}\)
\(x=\frac{47}{28}:2\) \(2x=-\frac{23}{28}:2\)
\(x=\frac{47}{56}\) \(2x=-\frac{23}{56}\)
\(\Rightarrow x\in\left\{\frac{47}{56};-\frac{23}{56}\right\}\)