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6 tháng 11 2021

Bài 1:

\(54\left(\dfrac{km}{h}\right)=15\left(\dfrac{m}{s}\right);9\left(\dfrac{m}{s}\right)=32,4\left(\dfrac{km}{h}\right)\)

Baì 2:

\(t'=s':v'=5:\left(5.3,6\right)=\dfrac{5}{18}h\)

\(\Rightarrow v_{tb}=\dfrac{s'+s''}{t'+t''}=\dfrac{5+3,8}{\dfrac{5}{18}+\left(\dfrac{15}{60}\right)}\simeq16,67\left(\dfrac{km}{h}\right)\)

6 tháng 11 2021

Nhường e cái lý 8 với ạ :((

Câu 2: 

\(\Leftrightarrow\left(x+2\right)\left(10x+3\right)=0\)

\(\Leftrightarrow\left[{}\begin{matrix}x=-2\\x=-\dfrac{3}{10}\end{matrix}\right.\)

2 tháng 10 2021

\(A1+2=A2\)

   \(\overline{A}\) =\(\dfrac{A1\cdot54+\cdot\left(A1+2\right)\cdot46}{100}\)=79.92

\(\Leftrightarrow\)A1=79\(\Rightarrow\)A2=81  

2 tháng 10 2021

Thanksss bann nhiều lắm nhoa

27 tháng 9 2021

1 When do they do their homework?

2 Who came to the party aloe

3 Which blouse do you like

4 How did she feel after she took a nap

5 How long did she talk to him

6 How many cars do your parents have

7 When are they coming to visit you?

8 Who is your brother

9 Why don't you get up early?

10 How often do you have an English class

15 tháng 7 2023

\(a.720:\left(x-17\right)=12\)

\(x-17=60\)

\(x=77\)

 

\(b.\left(x-28\right):12=8\)

\(x-28=96\)

\(x=124\)

 

\(c.26+8x=6x+46\)

\(8x-6x=46-26\)

\(2x=20\)

\(x=10\)

 

\(d.3600:\left[\left(5x+335\right):x\right]=50\)

\(\left(5x+335\right):x=72\)

\(5+335:x=72\)

\(335:x=67\)

\(x=5\)

15 tháng 7 2023

a) \(720:\left(x-17\right)=12\)

\(\Rightarrow x-17=\dfrac{720}{12}\)

\(\Rightarrow x-17=60\)

\(\Rightarrow x=60+17\)

\(\Rightarrow x=77\)

b) \(\left(x+28\right):12=8\)

\(\Rightarrow x+28=12\cdot8\)

\(\Rightarrow x+28=96\)

\(\Rightarrow x=96-28\)

\(\Rightarrow x=68\)

c) \(26+8x=6x+46\)

\(\Rightarrow8x-6x=46-26\)

\(\Rightarrow2x=20\)

\(\Rightarrow x=\dfrac{20}{2}\)

\(\Rightarrow x=10\)

d) \(3600:\left[\left(5x+335\right):x\right]=50\)

\(\Rightarrow\left(5x+335\right):x=\dfrac{3600}{50}\)

\(\Rightarrow\left(5x+335\right):x=72\)

\(\Rightarrow5x+335=72\cdot x\)

\(\Rightarrow72x-5x=335\)

\(\Rightarrow67x=335\)

\(\Rightarrow x=\dfrac{335}{67}\)

\(\Rightarrow x=5\)

NV
10 tháng 9 2021

Do \(\dfrac{a}{b}=\dfrac{c}{d}\Rightarrow\dfrac{b}{a}=\dfrac{d}{c}\)

\(\Rightarrow1-\dfrac{b}{a}=1-\dfrac{d}{c}\Rightarrow\dfrac{a-b}{a}=\dfrac{c-d}{c}\) (đpcm)