dễ mk bn cho mình hỏi nhé câu 4 là \(\frac{1}{2\cdot3}\)hay là\(\frac{1}{2}\cdot3\)

Cau 1

A=17/72     B=16      C=-5/21

Cau 2

a)    x=1      b)    -10/3

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

\(x-\dfrac{3}{4}=\dfrac{5}{7}\)

\(x=\dfrac{5}{7}+\dfrac{3}{4}=\dfrac{41}{28}\)

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) \(\dfrac{x}{2}=\dfrac{x}{3}=\dfrac{z}{5};xyz=-30\)

\(\dfrac{x}{2}=\dfrac{x}{3}=\dfrac{z}{5}=\dfrac{xyz}{2.3.5}=\dfrac{-30}{30}=-1\)

\(\Rightarrow\left\{{}\begin{matrix}x=2.\left(-1\right)=-2\\y=3.\left(-1\right)=-3\\z=5.\left(-1\right)=-5\end{matrix}\right.\)

a) �2=�5=�7;�+�+�=562x​=5y​=7z​;x+y+z=56

�2=�5=�7=�+�+�2+5+7=5614=42x​=5y​=7z​=2+5+7x+y+z​=1456​=4

⇒{�=4.2=8�=4.5=20�=4.7=28⇒⎩⎨⎧​x=4.2=8y=4.5=20z=4.7=28​

b) �1,1=�1,3=�1,4(1);2�−�=5,51,1x​=1,3y​=1,4z​(1);2x−y=5,5

(1)⇒2�−�1,1.2−1,3=5,50,9(1)⇒1,1.2−1,32x−y​=0,95,5​
    

⇒⎩⎨⎧​x=1,1.0,95,5​=0,96,05​y=1,3.0,95,5​=

chết rùi nó bị lỗi

xin lỗi nha

`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`

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

3/5x = 4/5 - 2/7

3/5x = 18/35

x = 18/35: 3/5

x = 6/7

\(a.\dfrac{3}{5}x-\dfrac{1}{2}=\dfrac{1}{7}\\ \dfrac{3}{5}x=\dfrac{1}{7}+\dfrac{1}{2}\\ \dfrac{3}{5}x=\dfrac{9}{14}\\ x=\dfrac{9}{14}:\dfrac{3}{5}\\ x=\dfrac{15}{14}\\ --------\\ b.\dfrac{3}{5}x+\dfrac{2}{7}=\dfrac{4}{5}\\ \dfrac{3}{5}x=\dfrac{4}{5}-\dfrac{2}{7}\\ \dfrac{3}{5}x=\dfrac{18}{35}\\ x=\dfrac{18}{35}:\dfrac{3}{5}\\ x=\dfrac{6}{7}\)

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

\(x=-\frac{32}{10}\)

Mn giúp mh với đg cần gấp lắm ln🥺🥺

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

a) \(x^2=100\)

\(=>x^2=10^2\)

\(=>x=10\)

b) \(\left(x-5\right)^2-7=9\)

\(=>\left(x-5\right)^2=9+7\)

\(=>\left(x-5\right)^2=16\)

\(=>\left(x-5\right)^2=4^2\)

\(=>x-5=4\)

\(=>x=4+5\)

\(=>x=9\)

2 bn lm thiếu rồi

a) x²=100

=> x = 10 hoặc -10

vậy............

b) ( x-5)²-7=9

=> ( x-5)² = 9 + 7

=> ( x-5)² = 16

+) ( x-5)² = 4²

=> x-5 = 4

=> x = 4+5

=>x=9

+) ( x-5)² = (-4)²

=> x-5 = -4

=> x = -4 + 5

=> x = 1

vậy x = 1 hoặc 9