PT chuyển động của 2 người :

\(\hept{\begin{cases}x_1=x_0+v_1t=10+4t\\x_2=v_2t=12t\end{cases}}\)

Khi 2 xe gặp nhau : \(x_1=x_2\)

Hay \(10+4t=12t\Leftrightarrow t=1,25h\)

=)) \(x_1=10+4t=10+4.1,25=15\left(km\right)\)

Vậy .... 

tham khao : https://hoc-24.vn/hoi-dap/question/59338.html

để tí gửi qua tin nhắn cho 

\(\left(3x+1\right)^2-9\left(x+2\right)^2=-5\)

\(\Leftrightarrow9x^2+6x+1-9\left(x^2+4x+4\right)=-5\)

\(\Leftrightarrow9x^2+6x+1-9x^2-36x-36=-5\)

\(\Leftrightarrow-30x-35=-5\Leftrightarrow-30x=30\Leftrightarrow x=-1\)

a, \(\left(x-y\right)\left(x+y\right)=x^2-y^2\)

\(\Leftrightarrow x^2+xy-xy-y^2=VP\Leftrightarrow x^2-y^2=VP\Leftrightarrow VT=VP\left(đpcm\right)\)

b, \(\left(x+y\right)^2=x^2+2xy+y^2\Leftrightarrow x^2+2xy+y^2=VP\Leftrightarrow VT=VP\left(đpcm\right)\)

c, \(\left(x-y\right)^2=x^2-2xy+y^2\Leftrightarrow x^2-2xy+y^2=VP\Leftrightarrow VT=VP\left(đpcm\right)\)

d, Ta có : \(\left(x+y\right)\left(x^2-xy+y^2\right)=x^3-x^2y+xy^2+x^2y-xy^2+y^3\)

\(=x^3+y^3=VP\Leftrightarrow VT=VP\left(đpcm\right)\)

e, Ta có : \(\left(x-y\right)\left(x^3+x^2y+xy^2+y^3\right)=x^4+x^3y+x^2y^2+xy^3-x^3y-x^2y^2-xy^3-y^4\)

\(=x^4-y^4=VP\Leftrightarrow VT=VP\left(đpcm\right)\)

1. Lan’s teacher wants her(spend) ………to spend………. more time on Math.

2. I promise I (try) ………will try……….. my best next semester.

3. Linh needs (improve) ……………in improve……….. her English writing.

4. They didn’t try (learn) ………to learn……… all new words they (come) ………came…….. across.

5. You should (underline) …underline………….the words you want (learn) ……to learn….. .

6. Can you help me (move) …………move………………… this table?

7. Minh always (get) …gets… grade A for Physics, but last semester he (get) …got…... So Minh’teacher asked him (study) ……………to study……… harder this semester.

8. They were proud of (be) ………being……… so successful.

9. He asked me (not wait) …………not to wait…………. For him.

10. You should (prace) ………prace…….. your English moer often.

Bài 4: Supply the correct form or tense of the verbs in breakets.

1. Lan’s teacher wants her(spend) ……to spend…………. more time on Math.

2. I promise I (try) …………will try…….. my best next semester.

3. Linh needs (improve) …………in improve………….. her English writing.

4. They didn’t try (learn) ………to learn……… all new words they (come) ……come……….. across.

5. You should (underline) ……underline……….the words you want (learn) ……….. .

6. Can you help me (move) …………move………………… this table?

7. Minh always (get) …gets… grade A for Physics, but last semester he (get) ……got... So Minh’teacher asked him (study) ………to study…………… harder this semester.

8. They were proud of (be) ………being……… so successful.

9. He asked me (not wait) …………not to wait…………. For him.

10. You should (prace) ……prace……….. your English moer often.

Hoa got used to ………… in her new school after a month.

A. study              B. studying         C. studied 　        D. is studying

2. Peter’s not going to drive, ………… he?

A. does               B. is                    C. isn’t 　             D. will

3. ………… the traffic was bad, they arrived on time.

A. Although         B. In spite of       C. Despite 　       D. Even

4. If you want to get more …………, please contact Mrs Hoa.

A. inform             B. informer          C. informative 　 D. information

5. Last Tuesday, my daughter was absent from school ………… of her illness.

A. because         B. instead            C. though            D. but

6. The headmaster asked me ………… for him outside his office.

A. wait                B. waiting             C. to wait 　        D. waited

7. He says he’s been to ………… restaurant in town.

A. many              B. every               C. all 　               D. most

8. My sister feels ………… again after her operation.

A. strongly          B. strength           C. strong 　        D. enough strong

Hoa got used to ………… in her new school after a month.

A. study              B. studying         C. studied 　        D. is studying

2. Peter’s not going to drive, ………… he?

A. does               B. is                    C. isn’t 　             D. will

3. ………… the traffic was bad, they arrived on time.

A. Although         B. In spite of       C. Despite 　       D. Even

4. If you want to get more …………, please contact Mrs Hoa.

A. inform             B. informer          C. informative 　 D. information

5. Last Tuesday, my daughter was absent from school ………… of her illness.

A. because         B. instead            C. though            D. but

6. The headmaster asked me ………… for him outside his office.

A. wait                B. waiting             C. to wait 　        D. waited

7. He says he’s been to ………… restaurant in town.

A. many              B. every               C. all 　               D. most

8. My sister feels ………… again after her operation.

A. strongly          B. strength           C. strong 　        D. enough strong

câu 1 á bro

Câu There are about 86 million people live in everywhere in Vietnam nha