Tìm x :
a)4/5 : x = 5/7
b)5/6 - 3/5 : x = 2/5
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KK
8 tháng 9 2021
a. \(\dfrac{5}{7}+\dfrac{4}{3}:x=\dfrac{1}{7}\)
<=> \(\dfrac{5}{7}+\dfrac{4}{3}.\dfrac{1}{x}=\dfrac{1}{7}\)
<=> \(\dfrac{5}{7}+\dfrac{4}{3x}=\dfrac{1}{7}\) ĐKXĐ: x \(\ne\) 0
<=> \(\dfrac{15x}{21x}+\dfrac{28}{21x}=\dfrac{3x}{21x}\)
<=> 15x + 28 = 3x
<=> 15x - 3x = -28
<=> 12x = -28
<=> x = \(\dfrac{-28}{12}=-\dfrac{7}{3}\)
b. \(\dfrac{5}{3}x.\dfrac{-1}{4}=\dfrac{2}{6}\)
<=> \(\dfrac{-5x}{12}=\dfrac{2}{6}\)
<=> -5x . 6 = 12 . 2
<=> -30x = 24
<=> x = \(-\dfrac{4}{5}\)
NT
2
28 tháng 2 2022
a: =-5/6-3/7=-35/42-18/42=-53/42
b: =18/45-20/45=-2/45
c: =-24/35
d: =2/3x-5/4=-10/12=-5/6
28 tháng 2 2022
\(\dfrac{-5}{6}+\dfrac{3}{7}=\dfrac{-5\times7+3\times6}{6\times7}=\dfrac{-17}{42}.\)
\(\dfrac{2}{5}-\dfrac{4}{9}=\dfrac{2\times9-4\times5}{5\times9}=\dfrac{-2}{45}.\)
\(\dfrac{-6}{5}\times\dfrac{4}{7}=\dfrac{-6\times4}{5\times7}=\dfrac{-24}{35}.\)
\(\dfrac{2}{3}:\dfrac{-4}{5}=\dfrac{2}{3}\times\dfrac{5}{-4}=\dfrac{-5}{6}.\)
SP
3
VT
12 tháng 2 2023
\(a,x-\dfrac{3}{4}=\dfrac{1}{7}\\ x=\dfrac{1}{7}+\dfrac{3}{4}\\ x=\dfrac{25}{28}\\ b,x+\dfrac{7}{5}=\dfrac{9}{8}.\dfrac{4}{27}\\ x+\dfrac{7}{5}=\dfrac{1}{6}\\ x=\dfrac{1}{6}-\dfrac{7}{5}\\ x=\dfrac{-37}{30}\\ c,\dfrac{2}{5}-\dfrac{3}{7}=\dfrac{x}{70}\\ \dfrac{-1}{35}=\dfrac{x}{70}\\ \dfrac{-2}{70}=\dfrac{x}{70}\\ x=-2\\ d,\dfrac{2}{9}-\dfrac{7}{8}.x=1\\ \dfrac{7}{8}.x=\dfrac{2}{9}-1\\ \dfrac{7}{8}.x=\dfrac{-7}{9}\\ x=\dfrac{-7}{9}:\dfrac{7}{8}\\ x=\dfrac{-8}{9}\)
Y
12 tháng 2 2023
\(a,x-\dfrac{3}{4}=\dfrac{1}{7}\)
\(\Rightarrow x=\dfrac{1}{7}+\dfrac{3}{4}\)
\(\Rightarrow x=\dfrac{25}{28}\)
\(b,x+\dfrac{7}{5}=\dfrac{9}{8}.\dfrac{4}{27}\)
\(\Rightarrow x+\dfrac{7}{5}=\dfrac{1}{6}\)
\(\Rightarrow x=\dfrac{1}{6}-\dfrac{7}{5}\)
\(\Rightarrow x=-\dfrac{37}{30}\)
\(c,\dfrac{2}{5}-\dfrac{3}{7}=\dfrac{x}{70}\)
\(\Rightarrow\dfrac{-1}{35}=\dfrac{x}{70}\)
\(\Rightarrow35x=-70\)
\(\Rightarrow x=-2\)
\(d,\dfrac{2}{9}-\dfrac{7}{8}.x=1\)
\(\Rightarrow\dfrac{7}{8}x=\dfrac{2}{9}-1\)
\(\Rightarrow\dfrac{7}{8}x=-\dfrac{7}{9}\)
\(\Rightarrow x=-\dfrac{8}{9}\)
12 tháng 3 2022
a, \(-4x+5+2x-1=3\Leftrightarrow-2x=-1\Leftrightarrow x=\dfrac{1}{2}\)
b, \(-2x+2=2\Leftrightarrow x=0\)
c, \(-2x-6=-8\Leftrightarrow x=1\)
NH
2
14 tháng 10 2021
\(\Rightarrow x^2-16-x^2+3x=5\)
\(\Rightarrow3x=21\Rightarrow x=7\)
=> Chọn A
a) x = 4/5 : 5/7
x = 28/25
b) 3/5 : x = 5/6 - 2/5
3/5 : x = 13/30
x = 3/5 : 13/30
x = 18/13
\(a,\Leftrightarrow x=\dfrac{4}{5}:\dfrac{5}{7}\)
\(\Leftrightarrow x=\dfrac{28}{25}\)
\(b,\Leftrightarrow\dfrac{3}{5}:x=\dfrac{13}{30}\)
\(\Leftrightarrow x=\dfrac{18}{13}\)