a) B= ( 5/7 .0,6 - 5: 7/2 ) . ( 40% - 1,4 ) . (-2 )³
b) 1/2 .x + 3/5 . ( x - 2 ) = 3
câu a là tính câu b là tìm x nhé, giúp mk vs
K
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TD
3 tháng 5 2017
dễ mk bn cho mình hỏi nhé câu 4 là \(\frac{1}{2\cdot3}\)hay là\(\frac{1}{2}\cdot3\)
ND
Nguyễn Đăng Nhân
CTVHS
18 tháng 9 2023
1. a
\(\dfrac{8}{5}-\dfrac{5}{6}\cdot\dfrac{3}{4}\)
\(=\dfrac{8}{5}-\dfrac{5\cdot3}{3\cdot2\cdot4}\)
\(=\dfrac{8}{5}-\dfrac{5}{8}=\dfrac{39}{40}\)
1.b
\(=\dfrac{7}{8}+\dfrac{5}{6}\cdot\dfrac{3}{2}\)
\(=\dfrac{7}{8}+\dfrac{5\cdot3}{3\cdot2\cdot2}\)
\(=\dfrac{7}{8}+\dfrac{5}{4}=\dfrac{17}{8}\)
2.a
\(\dfrac{4}{5}+x=\dfrac{11}{10}\)
\(x=\dfrac{11}{10}-\dfrac{4}{5}=\dfrac{3}{10}\)
2.b
\(x-\dfrac{3}{4}=\dfrac{5}{7}\)
\(x=\dfrac{5}{7}+\dfrac{3}{4}=\dfrac{41}{28}\)
ND
Nguyễn Đức Trí
VIP
19 tháng 7 2023
a) \(\dfrac{x}{2}=\dfrac{y}{5}=\dfrac{z}{7};x+y+z=56\)
\(\dfrac{x}{2}=\dfrac{y}{5}=\dfrac{z}{7}=\dfrac{x+y+z}{2+5+7}=\dfrac{56}{14}=4\)
\(\Rightarrow\left\{{}\begin{matrix}x=4.2=8\\y=4.5=20\\z=4.7=28\end{matrix}\right.\)
b) \(\dfrac{x}{1,1}=\dfrac{y}{1,3}=\dfrac{z}{1,4}\left(1\right);2x-y=5,5\)
\(\left(1\right)\Rightarrow\dfrac{2x-y}{1,1.2-1,3}=\dfrac{5,5}{0,9}\)
\(\Rightarrow\left\{{}\begin{matrix}x=1,1.\dfrac{5,5}{0,9}=\dfrac{6,05}{0,9}\\y=1,3.\dfrac{5,5}{0,9}=\dfrac{7,15}{0,9}\\z=\dfrac{1,4}{1,1}.x=\dfrac{1,4}{1,1}.\dfrac{6,05}{0,9}=\dfrac{8,47}{0,99}\end{matrix}\right.\)
d) \(\dfrac{x}{2}=\dfrac{x}{3}=\dfrac{z}{5};xyz=-30\)
\(\dfrac{x}{2}=\dfrac{x}{3}=\dfrac{z}{5}=\dfrac{xyz}{2.3.5}=\dfrac{-30}{30}=-1\)
\(\Rightarrow\left\{{}\begin{matrix}x=2.\left(-1\right)=-2\\y=3.\left(-1\right)=-3\\z=5.\left(-1\right)=-5\end{matrix}\right.\)
LB
4
2
23 tháng 4 2022
`a) 3 / 5 x - 1 / 2 = 1 / 7`
`3 / 5 x = 1 / 7 + 1 / 2`
`3 / 5 x = 9 / 14`
`x = 9 / 14 : 3 / 5`
`x = 15 / 14`
______________________________
`b) 3 / 5 x + 2 / 7 = 4 / 5`
`3 / 5 x = 4 / 5 - 2 / 7`
`3 / 5 x = 18 / 35`
`x = 18 / 35 : 3 / 5`
`x = 6 / 7`
15 tháng 6 2016
1/ a/\(-\frac{7}{18}=\left(-\frac{7}{2}\right)\left(\frac{1}{9}\right)\)
b/\(-\frac{7}{18}=\left(-\frac{7}{9}\right):2\)
2/
a/\(\frac{7}{15}\cdot\left(-\frac{3}{8}-\frac{3}{7}\right)=\frac{7}{15}\cdot\left(-\frac{45}{56}\right)=-\frac{3}{8}\)
b/\(\left(-\frac{3}{4}+\frac{2}{5}\right):\frac{3}{7}+\left(\frac{3}{5}+-\frac{4}{4}\right):\frac{3}{7}\)
\(=\left(-\frac{7}{20}\right):\frac{3}{7}+\left(-\frac{2}{5}\right):\frac{3}{7}\)
\(=\left(-\frac{49}{60}\right)+\left(-\frac{14}{15}\right)=-\frac{7}{4}\)
c/\(\frac{2}{3}\cdot\left(-\frac{5}{2}\right)+\frac{10}{15}\cdot\left(-\frac{3}{7}\right)-\frac{2}{3}\cdot\left(-\frac{5}{3}\right)\)
\(=\frac{2}{3}\cdot\left(-\frac{5}{2}-\frac{3}{7}+\frac{5}{3}\right)=-\frac{53}{63}\)
3/
\(2-\left(3-x\right)=-\frac{3}{2}\)
\(2-3+x=-\frac{3}{2}\)
\(x=-\frac{3}{2}+3-2=-\frac{1}{2}\)
4/
a/ Ta có 2 trường hợp:
TH1: \(x-3,5=7,5\)
\(x=7,5+3,5=11\)
TH2: \(x-3,5=-7,5\)
\(x=-7,5+3,5=-4\)
b/ Ta có 2 trường hợp:
TH1:\(x-0,4=3,6\)
\(x=4\)
TH2: \(x-0,4=-3,6\)
\(x=-3.2\)
c/ Ta có 2 trường hợp:
TH1:\(x+\frac{4}{5}=\frac{3}{2}\)
\(x=\frac{7}{10}\)
TH2:\(x+\frac{4}{5}=-\frac{3}{2}\)
\(x=-\frac{32}{10}\)
10 tháng 1 2018
1, Tìm x thuộc Z:
a) x2=100
=> x^2 = 10^2
=> x = 10
Vậy x = 10
b) ( x-5)2-7=9
=> ( x - 5 )^2 = 9 + 7
=> ( x - 5 )^2 = 16
=> ( x - 5 )^2 = 4 ^ 2
=> x - 5 = 4
=> x = 5 + 4
=> x = 9
kick nhé
10 tháng 1 2018
a) \(x^2=100\)
\(=>x^2=10^2\)
\(=>x=10\)
b) \(\left(x-5\right)^2-7=9\)
\(=>\left(x-5\right)^2=9+7\)
\(=>\left(x-5\right)^2=16\)
\(=>\left(x-5\right)^2=4^2\)
\(=>x-5=4\)
\(=>x=4+5\)
\(=>x=9\)
a,
\(B=\left(\dfrac{5}{7}\cdot0,6-5:\dfrac{7}{2}\right)\cdot\left(40\%-1,4\right)\cdot\left(-2\right)^3\\ =\left(\dfrac{5}{7}\cdot\dfrac{3}{5}-5\cdot\dfrac{2}{7}\right)\cdot\left(\dfrac{2}{5}-\dfrac{7}{5}\right)\cdot\left(-8\right)\\ =\left(\dfrac{3}{7}-\dfrac{10}{7}\right)\cdot\left(-1\right)\cdot\left(-8\right)\\ =\left(-1\right)\cdot\left(-1\right)\cdot\left(-8\right)\\ =\left(-8\right)\)
b,
\(\dfrac{1}{2}\cdot x+\dfrac{3}{5}\cdot\left(x-2\right)=3\\ \dfrac{1}{2}x+\dfrac{3}{5}x-\dfrac{6}{5}=3\\ x\left(\dfrac{1}{2}+\dfrac{3}{5}\right)=3+\dfrac{6}{5}\\ x\cdot\dfrac{11}{10}=\dfrac{21}{5}\\ x=\dfrac{21}{5}:\dfrac{11}{10}\\ x=\dfrac{42}{11}\\ Vậy......\)