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Bài 1:
a) Ta có: \(\frac{3}{5}+\frac{4}{15}\)
\(=\frac{9}{15}+\frac{4}{15}\)
\(=\frac{13}{15}\)
b) Ta có: \(\frac{-3}{5}+\frac{5}{7}\)
\(=\frac{-21}{35}+\frac{25}{35}=\frac{4}{35}\)
c) Ta có: \(\frac{5}{6}:\frac{-7}{12}\)
\(=\frac{5}{6}\cdot\frac{-12}{7}=\frac{-60}{42}=\frac{-10}{7}\)
d) Ta có: \(\frac{-21}{24}:\frac{-14}{8}\)
\(=\frac{-7}{8}:\frac{-7}{4}\)
\(=\frac{-7}{8}\cdot\frac{4}{-7}=\frac{4}{8}=\frac{1}{2}\)
e) Ta có: \(\frac{-3}{5}\cdot\frac{5}{7}+\frac{-3}{5}\cdot\frac{3}{7}+\frac{-3}{5}\cdot\frac{6}{7}\)
\(=\frac{-3}{5}\left(\frac{5}{7}+\frac{3}{7}+\frac{6}{7}\right)\)
\(=-\frac{3}{5}\cdot2=\frac{-6}{5}\)
f) Ta có: \(\frac{1}{3}\cdot\frac{4}{5}+\frac{1}{3}\cdot\frac{6}{5}-\frac{4}{3}\)
\(=\frac{1}{3}\cdot\frac{4}{5}+\frac{1}{3}\cdot\frac{6}{5}-\frac{1}{3}\cdot4\)
\(=\frac{1}{3}\left(\frac{4}{5}+\frac{6}{5}-4\right)\)
\(=\frac{1}{3}\cdot\left(-2\right)=\frac{-2}{3}\)
g) Ta có: \(\frac{4}{19}\cdot\frac{-3}{7}+\frac{-3}{7}\cdot\frac{5}{19}+\frac{5}{7}\)
\(=\frac{4}{19}\cdot\frac{-3}{7}+\frac{5}{19}\cdot\frac{-3}{7}+\frac{-3}{7}\cdot\frac{5}{-3}\)
\(=-\frac{3}{7}\left(\frac{4}{19}+\frac{5}{19}+\frac{-5}{3}\right)\)
\(=\frac{-3}{7}\cdot\left(\frac{27}{57}+\frac{-95}{57}\right)\)
\(=\frac{-3}{7}\cdot\frac{-68}{57}=\frac{68}{133}\)
h) Ta có: \(\frac{5}{9}\cdot\frac{7}{13}+\frac{5}{9}\cdot\frac{9}{13}-\frac{5}{9}\cdot\frac{3}{13}\)
\(=\frac{5}{9}\left(\frac{7}{13}+\frac{9}{13}-\frac{5}{13}\right)\)
\(=\frac{5}{9}\)
a) \(\frac{x}{3}-\frac{1}{4}=\frac{-5}{6}\)
\(\Rightarrow\frac{x}{3}=\frac{-5}{6}+\frac{1}{4}\)
\(\Rightarrow\frac{x}{3}=\frac{-7}{12}\)
\(\Rightarrow x=\frac{\left(-7\right).3}{12}\)
\(\Rightarrow x=\frac{-7}{4}\)
Vậy x = \(\frac{-7}{4}\)
b) \(\frac{x+3}{15}=\frac{1}{3}\)
\(\Rightarrow\left(x+3\right).3=15\)
\(\Rightarrow x+3=15:3\)
\(\Rightarrow x+3=5\)
\(\Rightarrow x=5-3\)
\(\Rightarrow x=2\)
Vậy x = 2
c) \(\frac{x-12}{4}=\frac{1}{2}\)
\(\Rightarrow\left(x-12\right).2=4\)
\(\Rightarrow x-12=4:2\)
\(\Rightarrow x-12=2\)
\(\Rightarrow x=2+12\)
\(\Rightarrow x=14\)
Vậy x = 14
d) \(\frac{25}{9}-\frac{12}{13}x=\frac{7}{9}\)
\(\Rightarrow\frac{12}{13}x=\frac{25}{9}-\frac{7}{9}\)
\(\Rightarrow\frac{12}{13}x=2\)
\(\Rightarrow x=2:\frac{12}{13}\)
\(\Rightarrow x=\frac{13}{6}\)
Vậy x = \(\frac{13}{6}\)
_Chúc bạn học tốt_
a)\(\frac{x}{3}-\frac{1}{4}=-\frac{5}{6}\)
\(\frac{x}{3}=-\frac{5}{6}+\frac{1}{4}\)
\(\frac{x}{3}=-\frac{7}{12}\)
\(x=-\frac{7}{12}\times3\)
\(\Rightarrow x=-\frac{7}{4}\)
b) \(\frac{x+3}{15}=\frac{1}{3}\)
\(\frac{x+3}{15\div5}=\frac{1}{3}\)
\(\Rightarrow x=5-3\)
\(\Rightarrow x=2\)
c) \(\frac{x-12}{4}=\frac{1}{2}\)
\(\frac{x-12}{4\div2}=\frac{1}{2}\)
\(x=12+2\)
\(\Rightarrow x=14\)
d) tự làm nhé cũng dễ mà
\(A=\frac{1}{3}.\frac{-9}{10}.\frac{-6}{13}.\frac{-13}{36}=\frac{-3}{10}.\frac{-1}{6}=\frac{1}{20}\)
\(B=\frac{4}{19}\left(\frac{-5}{12}+\frac{-7}{12}\right)-\frac{40}{57}=\frac{-4}{19}-\frac{40}{57}=\frac{-52}{57}\)
2 câu còn lại tự làm
\(A=\frac{1}{3}.\frac{-6}{13}.\frac{-9}{10}.\frac{-13}{36}\)
\(A=\frac{1}{1}.\frac{-2}{13}.\frac{-9}{10}.\frac{-13}{36}\)
\(A=\frac{-2}{13}.\frac{-9}{10}.\frac{-13}{36}\)
\(A=\frac{-1}{13}.\frac{-9}{5}.\frac{-13}{36}\)
\(A=\frac{-1}{13}.\frac{-1}{5}.\frac{-13}{4}\)
\(A=\frac{-13}{260}=\frac{-1}{20}\)
a
\(5\frac{4}{7}:x+=13\)
\(\frac{39}{7}:x=13\)
\(x=\frac{39}{7}:13\)
\(x=\frac{3}{7}\)
\(\frac{4}{7}x=\frac{9}{8}-0,125\)
\(\frac{4}{7}x=1\)
\(x=1:\frac{4}{7}\)
\(x=\frac{7}{4}=1\frac{3}{4}\)