a: Thay x=-4 vào B, ta được:

\(B=\dfrac{1-2\cdot\left(-4\right)}{2-\left(-4\right)}=\dfrac{1+8}{2+4}=\dfrac{9}{6}=\dfrac{3}{2}\)

\(=6x^2+45x-2x-7=6x^2+43x-7\)

ai giúp mình ik

\(3\left(2x+15\right)-\left(2x+7\right)=6x+45-2x-7=4x+38\)

a: S+O2->SO2

b: 4P+5O2->2P2O5

c: 3Fe+2O2->Fe3O4

d: 2Cu+O2->2CuO

e: 4Al+3O2->2Al2O3

1. b

2. 2 hình ảnh so sánh: "một quả bồ câu ... phía dưới" và "một quả cầu ... vạn vật".

b) Vì \(\hept{\begin{cases}2a=3b\\4b=5c\end{cases}}\Rightarrow\hept{\begin{cases}\frac{a}{3}=\frac{b}{2}\\\frac{b}{5}=\frac{c}{4}\end{cases}}\)  \(\Rightarrow\hept{\begin{cases}\frac{a}{15}=\frac{b}{10}\\\frac{b}{10}=\frac{c}{8}\end{cases}}\Rightarrow\frac{a}{15}=\frac{b}{10}=\frac{c}{8}\)

Áp dụng tính chất dãy tỉ số bằng nhau , ta có :

\(\frac{a}{15}=\frac{b}{10}=\frac{c}{8}=\frac{2a}{30}=\frac{2c}{16}=\frac{2a-b-2c}{30-10-16}=\frac{4}{4}=1\)

\(\Rightarrow\hept{\begin{cases}a=15\\b=10\\c=8\end{cases}}\)

Câu 5 :

Vì \(\hept{\begin{cases}a=2b\\b=3c\end{cases}}\Rightarrow\hept{\begin{cases}\frac{a}{2}=\frac{b}{1}\\\frac{b}{3}=\frac{c}{1}\end{cases}}\)\(\Rightarrow\hept{\begin{cases}\frac{a}{6}=\frac{b}{3}\\\frac{b}{3}=\frac{c}{1}\end{cases}}\Rightarrow\frac{a}{6}=\frac{b}{3}=\frac{c}{1}\)

Áp dụng tính chất dãy tỉ số bằng nhau , ta có :

\(\frac{a}{6}=\frac{b}{3}=\frac{c}{1}=\frac{2b}{6}=\frac{3c}{3}=\frac{a-2b+3c}{6-6+3}=\frac{6}{3}=2\)

\(\Rightarrow\hept{\begin{cases}a=2.6=12\\b=2.3=6\\c=2.1=2\end{cases}}\)

\(a,\hept{\begin{cases}a=2b\\b=3c\\a-2b+3c=6\end{cases}}\)

\(a-a+b=6\)

\(b=6\)

\(\Rightarrow\hept{\begin{cases}a=2b=2.6=12\\b=3c=3.6=18\end{cases}}\)

Vậy ... 

Task 2. Write one word to complete the sentence:

1. What ‘s the ………matter……..with you?

2. How ………many…………… subjects do you have today?

3. My mother …………works….…..in factories.

4. Where …………will….…you go next weekend?

5. My friends …………play………… badminton in their free time.

6. I often ………get….……up early in the morning.

7. She …………doesn't/ does not…..…. go to the dentist.

8. …………Did……..….you join the funfair last Sunday?

9. What ………time…….… do you go to school?

10. I like ………playing………. the piano.

Task 2. Write one word to complete the sentence:

1. What ‘s the ………matter………..with you?

2. How …………many………… subjects do you have today?

3. My mother ……works……….…..in factories.

4. Where ………will…….…you go next weekend?

5. My friends ………play…………… badminton in their free time.

6. I often ………get….……up early in the morning.

7. She …………doesn't…..…. go to the dentist.

8. ………Did………..….you join the funfair last Sunday?

9. What ………time…….… do you go to school?

10. I like ………to play………. the piano.

1. What ‘s the ……matter…………..with you?

2. How …………many………… subjects do you have today?

3. My mother ………works…….…..in factories.

4. Where …………will….…you go next weekend?

5. My friends ………play…………… badminton in their free time.

6. I often ………get….……up early in the morning.

7. She ………will……..…. go to the dentist.

8. …………Did……..….you join the funfair last Sunday?

9. What ………time…….… do you go to school?

10. I like ………playing………. the piano.

38. My sister is fond of listening to music in her free time. 

39. You should add coconut to cook the best five-coloured sticky rice.

Rewrite sentences without changing the meaning

Question 11: I find cooking in my free time relaxing.

A. It’s relaxing to me to cook in my free time.

B. Cooking is relaxing for free time.

C. Free time relaxing is cooking.

D. I spend cooking my free time.

Question 12: I close friend gave me a wonderful present on my birthday

A. I gave my friend a wonderful present on my birthday.

B. I was given a wonderful present on my birthday.

C. A wonderful present was given me on my birthday.

D. My birthday gave a wonderful present.

Question 13: Skateboarding is her hobby.

A. She doesn’t like skateboarding.

B. Skateboarding is fun.

C. Hobby includes skateboarding.

D. Her favourite leisure activity is skateboarding.

Question 14: He likes to listen to pop music than to watch TV after school.

A. He prefers listening to pop music to watching TV after school.

B. He like watching TV more than listening to music after school.

C. Listening to pop music is more exciting than watching TV.

D. Watching TV is less interesting than listening to pop music.

Question 15: My parents insist me on learning Spanish.

A. My parents want me to study Spanish.

B. My parents teach me to study Spanish.

C. My parents make me to study Spanish.

D. My parents remind me to study Spanish.

a

b

d

a

a