1 Your sister is interested in doing DIY in her free time, isn't she?

2 Unless that girl study harder, she will fail the exam

3 My father has given up smoking since last year

4 Mary wanted to know what Peter would give his brother on his birthday the day after

1. Your sister is interested in doing DIY in her free time, isn't she?

2. Unless that girl studies harder, she'll fail the exam.

3. My father has given up smoking since last year.

4. Mary wanted to know what Peter would give his brother on his birthday the next day.

Câu 4: 

\(\dfrac{3x+5}{16}-\dfrac{3x-5}{26}=\dfrac{3x-8}{29}-\dfrac{3x+8}{13}\)

\(\Leftrightarrow\left(\dfrac{3x+5}{16}+1\right)-\left(\dfrac{3x-5}{26}+1\right)=\left(\dfrac{3x-8}{29}+1\right)-\left(\dfrac{3x-8}{13}+1\right)\)

\(\Leftrightarrow\left(3x+21\right)\left(\dfrac{1}{16}-\dfrac{1}{26}-\dfrac{1}{29}+\dfrac{1}{13}\right)=0\)

=>3x+21=0

hay x=-7

\(\left(\dfrac{1}{3}\right)^4:\left(-\dfrac{9}{2}\right)^6\)

\(=\dfrac{1}{3^4}:\dfrac{3^{12}}{2^6}\)

\(=\dfrac{2^6}{3^{16}}\)

=\(\dfrac{1}{3^4}\):\(\dfrac{3^{12}}{2^6}\)

=\(\dfrac{2^6}{3^{16}}\)

câu 11 là c 

câu 9 là b

câu 8 là b 

1. D

2. A

3. D

4. B

5. B

6. A

7. C

8. B

9. B

10. C

11. C

12. D

2 D 4 B 6A 8B 9A 10C 11 C

Hình:

ABC68HD

~~~

a/ A/dụng pitago vào tam giác ABC v tại A có:

BC2=AB2+AC2=62+82=100⇒BC=10(cm)BC2=AB2+AC2=62+82=100⇒BC=10(cm)

Áp dụng hệ thức lượng trong tam giác v ABC có:

+) AB2 = BC . BH => BH=AB2BC=3610=3,6(cm)BH=AB2BC=3610=3,6(cm)

=> HC = BC - BH = 10 - 3,6 = 6,4(cm)

+) AH2 = BH . HC = 3,6 . 6,4 = 23,04

=> AH = 4,8 (cm)

b/ Vì AD là p/g góc BAC

=> BDDC=ABAC⇒BDAB=DCAC=BD+DCAB+AC=BC6+8=106+8=57BDDC=ABAC⇒BDAB=DCAC=BD+DCAB+AC=BC6+8=106+8=57

=> ⎧⎩⎨⎪⎪⎪⎪BD=57⋅6=307(cm)DC=57⋅8=407(cm)

 Chúc bạn hok tốt ^^

By Ryu