Bài tập cuối chương 1

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Tìm x, biết:

a)−\(\dfrac{3}{5}\).x=\(\dfrac{12}{25}\);

b)\(\dfrac{3}{5}\)x−\(\dfrac{3}{4}\)=−1\(\dfrac{1}{2}\);

c)\(\dfrac{2}{5}\)+\(\dfrac{3}{5}\):x=0,5;

d)\(\dfrac{3}{4}\)−(x−\(\dfrac{1}{2}\))=1\(\dfrac{2}{3}\)

e)2\(\dfrac{2}{15}\):(\(\dfrac{1}{3}\)−5x)=−2\(\dfrac{2}{5}\)

g)x2+\(\dfrac{1}{9}\)=\(\dfrac{5}{3}\):3.

 

Vanh Nek
21 tháng 11 2022 lúc 18:39

a)

\(-\dfrac{3}{5}.x=\dfrac{12}{25}\)

\(x=\dfrac{12}{25}:\left(-\dfrac{3}{5}\right)\)

\(x=\dfrac{12}{25}.\dfrac{-5}{3}\)

\(x=\dfrac{-4}{5}\)

b)

\(\dfrac{3}{5}x-\dfrac{3}{4}=-1\dfrac{1}{2}\)

\(\dfrac{3}{5}x-\dfrac{3}{4}=\dfrac{-3}{2}\)

\(\dfrac{3}{5}x=\dfrac{-3}{2}+\dfrac{3}{4}\)

\(\dfrac{3}{5}x=\dfrac{-6}{4}+\dfrac{3}{4}\)

\(\dfrac{3}{5}x=\dfrac{-3}{4}\)

\(x=\dfrac{-3}{4}:\dfrac{3}{5}\)

\(x=\dfrac{-3}{4}.\dfrac{5}{3}\)

\(x=\dfrac{-5}{4}\)

c)

\(\dfrac{2}{5}+\dfrac{3}{5}:x=0,5\)

\(\dfrac{2}{5}+\dfrac{3}{5}:x=\dfrac{1}{2}\)

\(\dfrac{3}{5}:x=\dfrac{1}{2}-\dfrac{2}{5}\)

\(\dfrac{3}{5}:x=\dfrac{5}{10}-\dfrac{4}{10}\)

\(\dfrac{3}{5}:x=\dfrac{1}{10}\)

\(x=\dfrac{3}{5}:\dfrac{1}{10}\)

\(x=\dfrac{3}{5}.\dfrac{10}{1}\)

\(x=6\)

d)

\(\dfrac{3}{4}-\left(x-\dfrac{1}{2}\right)=1\dfrac{2}{3}\)

\(\dfrac{3}{4}-\left(x-\dfrac{1}{2}\right)=\dfrac{5}{3}\)

\(x-\dfrac{1}{2}=\dfrac{3}{4}-\dfrac{5}{3}\)

\(x-\dfrac{1}{2}=\dfrac{9}{12}-\dfrac{20}{12}\)

\(x-\dfrac{1}{2}=\dfrac{-11}{12}\)

\(x=\dfrac{-11}{12}+\dfrac{1}{2}\)

\(x=\dfrac{-11}{12}+\dfrac{6}{12}\)

\(x=\dfrac{-5}{12}\)

e)

\(2\dfrac{2}{15}:\left(\dfrac{1}{3}-5x\right)=-2\dfrac{2}{5}\)

\(\dfrac{32}{15}:\left(\dfrac{1}{3}-5x\right)=\dfrac{-12}{5}\)

\(\dfrac{1}{3}-5x=\dfrac{32}{15}:\dfrac{-12}{5}\)

\(\dfrac{1}{3}-5x=\dfrac{32}{15}.\dfrac{-5}{12}\)

\(\dfrac{1}{3}-5x=\dfrac{-8}{9}\)

\(5x=\dfrac{1}{3}-\dfrac{-8}{9}\)

\(5x=\dfrac{3}{9}+\dfrac{8}{9}\)

\(5x=\dfrac{11}{9}\)

\(x=\dfrac{11}{9}:5\)

\(x=\dfrac{11}{45}\)

g)

\(x^2+\dfrac{1}{9}=\dfrac{5}{3}:3\)

\(x^2+\dfrac{1}{9}=\dfrac{5}{9}\)

\(x^2=\dfrac{5}{9}-\dfrac{1}{9}\)

\(x^2=\dfrac{4}{9}\)

\(x^2=\left(\dfrac{2}{3}\right)^2\) hoặc \(x^2=\left(-\dfrac{2}{3}\right)^2\)

Nên \(\Rightarrow x=\dfrac{2}{3}\) hoặc \(x=-\dfrac{2}{3}\)

le phong
15 tháng 7 2023 lúc 11:03

a) x=−35−35

x=3535x=3434

−34−34

x=3535

x=3535:x=0,5-3535:x=3535:1212)=2323

(x-3434-11212)=−1112−1112+−1712−1712

e) 215215:(-21313-5x=1313-119119

x=11451145

g) x2+5959

x2=1919

x2=√4949

x=