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Bài 4: 

a) Xét ΔHBA vuông tại H và ΔABC vuông tại A có 

\(\widehat{ABC}\) chung

Do đó: ΔHBA\(\sim\)ΔABC(g-g)

c) Áp dụng định lí Pytago vào ΔABC vuông tại A, ta được:

\(BC^2=AB^2+AC^2\)

\(\Leftrightarrow BC^2=12^2+16^2=400\)

hay BC=20(cm)

Vậy: BC=20cm

Bài 4: 

\(x=130^0\)

4 tháng 12 2021

cụ thể hơn đc ko ạ

NV
6 tháng 1 2022

\(3x\left(x-y\right)+x-y\)

\(=3x\left(x-y\right)+1\left(x-y\right)\)

\(=\left(x-y\right)\left(3x+1\right)\)

\(=\left(x-y\right)\left(3x+1\right)\)

5 tháng 7 2021

1 are

2 am

3 is

4 are

5 are

6 are

7 is

8 is

9 is

10 are

IV

1 is writing

2 are losing

3 is having

4 is staying

5 am not lying

6 is always using

7 are having

8 Are you playing

9 are not touching

10 Is - listening

11 Is- winning

12 am not staying

13 is not working

14 is not reading

15 isn't raining

16 am not listening

17 Are they making

18 Are you doing

19 Is - sitting

20 is - doing

21 are-putting

22 are-wearing

23 is-studying

5 tháng 7 2021

2, am

3, is

4,are

5,are

6,are

7,is

8,is

9,is

10,are

IV

1,2,7 OK

3,is having

4,has stayed

5,am not lying

6,always uses

8,Are-playing

9,not to touch

10,Is-listening

11,Are-winning

12,am not staying

13,isn't working

14,isn't reading

15,isn't raining

16,am not listening

17,Are-making

18,Are-doing

19,Is-sitting

20,is-doing

21,do-putting

22,do-wear

23,is-studying

1) 

\(4Fe+3O_{2\left(dư\right)}\xrightarrow[]{t^o}2Fe_2O_3\)

\(Fe_2O_3+6HCl\rightarrow2FeCl_3+3H_2O\)

\(FeCl_3+3KOH\rightarrow Fe\left(OH\right)_3\downarrow+3KCl\)

\(2Fe\left(OH\right)_3\xrightarrow[]{t^o}Fe_2O_3+3H_2O\)

\(Fe_2O_3+CO\xrightarrow[]{500-600^oC}2FeO+CO_2\)

17 tháng 4 2022

\(\left|2x-3\right|=3-2x\)

\(ĐK:x\le\dfrac{3}{2}\)

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

\(\Leftrightarrow\left[{}\begin{matrix}x=\dfrac{3}{2}\\0=0\left(đúng\right)\end{matrix}\right.\)

Vậy \(S=\left\{x\in R;x=\dfrac{3}{2}\right\}\)

2 tháng 7 2021

2 do

3 usually buy

4 press

5 enjoy

6 has

7 goes

8 gets

9 eat

10 doesn't study

11 doesn't eat

12 doesn't water

13 don't go

14 doesn't eat - is

15 Do - go

16 Do - agree

17 Do you have

18 Do you often eat

19 Does - start

20 does he come

21 does - work

22 does

23 does - do

24 does- go

2 tháng 7 2021

Cảm ơn ạ!haha

14 tháng 5 2022

My grandma often works in the garden in her free time.

What are you doing with the stove?

14 tháng 5 2022

3. My grandma often works in the garden in her free time.

4. What are you doing with the stove?