Question

[Em học dốt]

\(\frac{1}{2}+\frac{5}{6}-\frac{3}{8}\)

\(\frac{10}{15}.\frac{7}{4}+\frac{7}{4}.\frac{9}{15}-\frac{4}{15}.\frac{7}{4}\)

\(\left(\frac{4}{5}+\frac{1}{2}\right).\left(\frac{3}{13}-\frac{8}{13}\right)\)

Tìm số nguyên x, bt:

a/ 3x-12=30                       b/

\(\frac{2}{3}x+\frac{1}{4}=\frac{7}{12}\)

c/ 2x² =32

giúp em nhé mai em thi!

Answer 1

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\(\frac{1}{2}+\frac{5}{6}-\frac{3}{8}\)

\(=\frac{12}{24}+\frac{20}{24}-\frac{9}{24}\)

\(=\frac{23}{24}\)

\(\frac{10}{15}\cdot\frac{7}{4}+\frac{7}{4}\cdot\frac{9}{15}-\frac{4}{15}\cdot\frac{7}{4}\)

\(=\frac{7}{4}\cdot\left(\frac{10}{15}+\frac{9}{15}-\frac{4}{15}\right)\)

\(=\frac{7}{4}\cdot1=\frac{7}{4}\)

\(\left(\frac{4}{5}+\frac{1}{2}\right)\left(\frac{3}{13}-\frac{8}{13}\right)\)

\(=\left(\frac{8}{10}+\frac{5}{10}\right)\cdot\left(-\frac{5}{13}\right)\)

\(=\frac{13}{10}\cdot\left(-\frac{5}{13}\right)=-\frac{1}{2}\)

Answer 2

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a,  3x-12 = 30 

=> 3x = 30 + 12

=> 3x = 42 

=> x = 42 : 3  = 14 

Vậy x = 14 

b, \(\frac{2}{3}x+\frac{1}{4}=\frac{7}{12}\)

\(\Rightarrow\frac{2}{3}x=\frac{7}{12}-\frac{1}{4}\)

\(\Rightarrow\frac{2}{3}x=\frac{7}{12}-\frac{3}{12}\)

\(\Rightarrow\frac{2}{3}x=\frac{1}{3}\)

\(\Rightarrow x=\frac{1}{3}\div\frac{2}{3}\Rightarrow\frac{1}{3}\cdot\frac{3}{2}=\frac{1}{2}\)

Vậy x = \(\frac{1}{2}\)

c, 2x² = 32 

=> x² = 32 : 2 

=> x² = 16

=> x² = 4² 

=> x = 4 

Vậy x = 4