Question

Bài 1: Tìm x, biết

a,\(\dfrac{1}{2}+\dfrac{2}{3}.x=\dfrac{4}{5}\)

b,\(x+\dfrac{1}{4}=\dfrac{4}{3}\)

c,\(\dfrac{3}{5}x-\dfrac{1}{2}=-\dfrac{1}{7}\)

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

e,\(\dfrac{1}{2}-lxl=\dfrac{1}{3}\)

Answer 1

a, \(\dfrac{1}{2}+\dfrac{2}{3}x=\dfrac{4}{5}\)

\(\Rightarrow\dfrac{2}{3}x=\dfrac{4}{5}-\dfrac{1}{2}\\ \Rightarrow\dfrac{2}{3}x=\dfrac{3}{10}\\ \Rightarrow x=\dfrac{3}{10}\cdot\dfrac{3}{2}\\ \Rightarrow x=\dfrac{9}{20}\)

b, \(x+\dfrac{1}{4}=\dfrac{4}{3}\)

\(\Rightarrow x=\dfrac{4}{3}-\dfrac{1}{4}\\ \Rightarrow x=\dfrac{13}{12}\)

c, \(\dfrac{3}{5}x-\dfrac{1}{2}=-\dfrac{1}{7}\)

\(\Rightarrow\dfrac{3}{5}x=-\dfrac{1}{7}-\dfrac{1}{2}\\ \Rightarrow\dfrac{3}{5}x=-\dfrac{9}{14}\\ \Rightarrow x=-\dfrac{9}{14}\cdot\dfrac{5}{3}\\ \Rightarrow x=\dfrac{15}{14}\)

d, \(\left|x-\dfrac{4}{5}\right|=\dfrac{3}{4}\)

\(\Rightarrow\left\{{}\begin{matrix}x-\dfrac{4}{5}=\dfrac{3}{4}\\x-\dfrac{4}{5}=-\dfrac{3}{4}\end{matrix}\right.\Rightarrow\left\{{}\begin{matrix}x=\dfrac{3}{4}+\dfrac{4}{5}\\x=-\dfrac{3}{4}+\dfrac{4}{5}\end{matrix}\right.\Rightarrow\left\{{}\begin{matrix}x=\dfrac{31}{20}\\x=\dfrac{1}{20}\end{matrix}\right.\)

e, \(lxl\) là j mk ko hiểu!

Answer 2

a)2/3x=4/5-1/2

2/3x=3/10

x=3/10:2/3= 3/10.3/2=9/20