Bài 1:
a) 8/7 . 2/3 - 5/6 . 16/14
b) x + 3/8 = 12/5 - 3/4
c) x . 8/7 = 4/8 - 3/5 . 2/4
d) 12/5 - ( x + 1/3 ) = 3/7 : 4/6
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19 tháng 3 2020
nhiều quá :((
\(a,2\left(x-5\right)-3\left(x+7\right)=14\)
\(2x-10-3x-21=14\)
\(-x-31=14\)
\(-x=45\)
\(x=45\)
\(b,5\left(x-6\right)-2\left(x+3\right)=12\)
\(5x-30-2x-6=12\)
\(3x-36==12\)
\(3x=48\)
\(x=16\)
\(c,3\left(x-4\right)-\left(8-x\right)=12\)
\(3x-12-8+x=0\)
\(4x-20=0\)
\(4x=20\)
\(x=5\)
Cố nốt nha bn !
LM
19 tháng 3 2020
cảm ơn, bn nha:)))
mà hình như bạn TOP 3 trả lời câu hỏi pải ko nhỉ???
14 tháng 6 2023
a: =7/8:(2/9-18+1/36)-5/12
=-7/142-5/12=-397/852
b: =3/7(4/9+5/9:6/12)=2/3
c: =5^8(16/31-47/31)+1/3=-5^8+1/3
d: =7/2(3/8+5/8:4/15)=609/64
27 tháng 7 2021
a) Ta có: \(\dfrac{-5}{7}\left(\dfrac{14}{5}-\dfrac{7}{10}\right):\left|-\dfrac{2}{3}\right|-\dfrac{3}{4}\left(\dfrac{8}{9}+\dfrac{16}{3}\right)+\dfrac{10}{3}\left(\dfrac{1}{3}+\dfrac{1}{5}\right)\)
\(=\dfrac{-5}{7}\cdot\dfrac{3}{2}\cdot\dfrac{21}{10}-\dfrac{3}{4}\cdot\dfrac{56}{3}+\dfrac{10}{3}\cdot\dfrac{8}{15}\)
\(=\dfrac{-9}{4}-14+\dfrac{16}{9}\)
\(=\dfrac{-1621}{126}\)
b) Ta có: \(\dfrac{17}{-26}\cdot\left(\dfrac{1}{6}-\dfrac{5}{3}\right):\dfrac{17}{13}-\dfrac{20}{3}\left(\dfrac{2}{5}-\dfrac{1}{4}\right)+\dfrac{2}{3}\left(\dfrac{6}{5}-\dfrac{9}{2}\right)\)
\(=\dfrac{-17}{26}\cdot\dfrac{13}{17}\cdot\dfrac{-3}{2}-\dfrac{20}{3}\cdot\dfrac{3}{20}+\dfrac{2}{3}\cdot\dfrac{-33}{10}\)
\(=\dfrac{3}{4}-1-\dfrac{11}{5}\)
\(=-\dfrac{49}{20}\)
2 tháng 7 2018
b, 3/5 + 4/7 + 2/8 + 10/25 + 9/21 + 28/16
= 3/5 + 4/7 + 2/8 + 2/5 + 3/7 + 14/8
= (3/5 + 2/5) + ( 4/7 + 3/7) + ( 2/8 + 14/8)
= 1 + 1 + 7/4
= 2 + 7/4 = 15/4
c , 8/7 + 7/6 + 5/8 + 10/12 + 24/28 + 6/16
= c , 8/7 + 7/6 + 5/8 + 5/6 + 6/7 + 1/2
= (8/7 + 6/7) + (7/6 + 5/6) + 5/8 + 1/2
= 14/7 + 12/6 + 5/8 + 1/2
= 2 + 2 + 5/8 + 1/2
= 4 + 9/8 = 41/8
20 tháng 12 2020
Bai 2 :
\(\hept{\begin{cases}x+y=7\\x-7=13\end{cases}\Leftrightarrow\hept{\begin{cases}x+y=7\\x=20\end{cases}}}\)
Thay x vào phương trình đầu ta có :
\(20+y=7\Leftrightarrow y=-13\)
Vậy \(\left\{x;y\right\}=\left\{20;-13\right\}\)
Thử \(20-13=7\); \(20-7=13\)( thỏa mãn )
a, \(\dfrac{8}{7}\) x \(\dfrac{2}{3}\) - \(\dfrac{5}{6}\)x \(\dfrac{16}{14}\)
= \(\dfrac{16}{21}\) - \(\dfrac{20}{21}\)
= - \(\dfrac{4}{21}\)
b, x + \(\dfrac{3}{8}\) = \(\dfrac{12}{5}\) - \(\dfrac{3}{4}\)
x + \(\dfrac{3}{8}\) = \(\dfrac{33}{20}\)
x = \(\dfrac{33}{20}\) - \(\dfrac{3}{8}\)
x = \(\dfrac{51}{40}\)
c, x . \(\dfrac{8}{7}\) = \(\dfrac{4}{8}\) - \(\dfrac{3}{5}\) . \(\dfrac{2}{4}\)
x. \(\dfrac{8}{7}\) = \(\dfrac{1}{2}\) - \(\dfrac{3}{10}\)
x. \(\dfrac{8}{7}\) = \(\dfrac{1}{5}\)
x = \(\dfrac{1}{5}\) : \(\dfrac{8}{7}\)
x = \(\dfrac{1}{5}\) x \(\dfrac{7}{8}\)
x = \(\dfrac{7}{40}\)
d, \(\dfrac{12}{5}\) - ( x + \(\dfrac{1}{3}\)) = \(\dfrac{3}{7}\) : \(\dfrac{4}{6}\)
\(\dfrac{12}{5}\) - (x + \(\dfrac{1}{3}\)) = \(\dfrac{9}{14}\)
x + \(\dfrac{1}{3}\) = \(\dfrac{12}{5}\) - \(\dfrac{9}{14}\)
x + \(\dfrac{1}{3}\) = \(\dfrac{123}{70}\)
x = \(\dfrac{123}{70}\) - \(\dfrac{1}{3}\)
x = \(\dfrac{299}{210}\)