lỗi latex=copy

`81^8=3^x`

`=>3^x=(3^4)^8`

`=>3^x=3^32`

`=>x=32`

Vậy `x=32`

Hmm, nói đến cờ chắc là dấu hiệu của semaphore, thử mò xem :v

a) \(\left|7x-4\right|=-7\)

Mà \(\left|7x-4\right|\ge0\forall x\)

\(\Rightarrow\) phương trình vô nghiệm

b) \(\left|3x-4\right|=\left|7x+5\right|\)

\(\Rightarrow\left[{}\begin{matrix}3x-4=7x+5\\3x-4=-7x-5\end{matrix}\right.\)

\(\Rightarrow\left[{}\begin{matrix}x=-\dfrac{9}{4}\\x=-\dfrac{1}{10}\end{matrix}\right.\)

Vậy ...

tách 

1 A

2 D

3 B

4 D

1 She is really worried that she won't pass the final exam

2 I am so pleased that my favorite team won

3 The wolf pretended to be the girl's grandma

4 You don't remember to set your alarm clock so you oversleep

5 Julia arrived at the airport late because of the traffic jam

a: \(VP=a^3+b^3+c^3-3bac\)

\(=\left(a+b\right)^3+c^3-3ab\left(a+b\right)-3abc\)

\(=\left(a+b+c\right)\left[\left(a+b\right)^2-c\left(a+b\right)+c^2\right]-3ab\left(a+b+c\right)\)

\(=\left(a+b+c\right)\left(a^2+2ab+b^2-ac-bc+c^2-3ab\right)\)

\(=\left(a+b+c\right)\left(a^2+b^2+c^2-ab-bc-ac\right)=VT\)

b: \(VT=\left(3a+2b-1\right)\left(a+5\right)-2b\left(a-2\right)\)

\(=3a^2+15a+2ab+10b-a-5-2ab+4b\)

\(=3a^2+14a+14b-5\)

\(VP=\left(3a+5\right)\left(a+3\right)+2\left(7b-10\right)\)

\(=3a^2+9a+5a+15+14b-20\)

\(=3a^2+14a+14b-5\)

=>VT=VP

c: \(VT=a\left(b-x\right)+x\left(a+b\right)\)

\(=ab-ax+ax+bx\)

\(=ab+bx=b\left(a+x\right)=VP\)

d: \(VT=a\left(b-c\right)-b\left(a+c\right)+c\left(a-b\right)\)

\(=ab-ac-ab-bc+ca-cb\)

\(=-2bc\)

=VP

B1

1. is

2. is

3. are

4. is

5. is/ am

6. aren't

7. are

8. Is she

9. is

10. are

B2

5. doesn't

7. don't

8. doesn't

9. don't

10. don't

B3

1. starts

2. likes

3. bake

4. writes

5. doesn't know

6. has

7. swim

8. helps 

-----------

CT thì hiện tại đơn:

(+) S + V(s/es) + O

(-) S + don't/ doesn't + V + O

(?) Do/Does + S + V + O?

Tobe: am/is/are

- Nếu chủ ngữ là số ít, he, she, it thì tobe là is và V phải thêm s/es.

- Nếu chủ ngữ là số nhiều, you, we, they thì to be là are và V giữ nguyên.

- Nếu chủ ngữ là I thì tobe là am và V cũng giữ nguyên.

Câu 5: 

\(\Leftrightarrow-x^2+7x-9+2x-9=0\)

\(\Leftrightarrow x^2-9x+18=0\)

=>x=3

=>Chọn A