có : (67 - 15) :1 +1= 53

a) \(\dfrac{1}{2}.\left(\dfrac{2}{9}+\dfrac{3}{7}-\dfrac{5}{27}\right)\)

\(=\dfrac{1}{2}.\left(\dfrac{41}{63}-\dfrac{5}{27}\right)\)

\(=\dfrac{1}{2}.\dfrac{88}{189}\)

\(=\dfrac{44}{189}\)

b) \(\left(\dfrac{-5}{28}+1,75+\dfrac{8}{35}\right):\left(-3\dfrac{9}{20}\right)\)

\(=\left(\dfrac{11}{7}+\dfrac{8}{35}\right):\left(-3\dfrac{9}{20}\right)\)

\(=\dfrac{9}{5}:\left(-3\dfrac{9}{20}\right)\)

\(=\dfrac{9}{5}:\dfrac{-69}{20}\)

\(=\dfrac{-12}{23}\)

c) \(\dfrac{1}{3}.\dfrac{5}{7}-\dfrac{7}{27}.\dfrac{36}{14}\)

\(=\dfrac{5}{21}-\dfrac{7}{27}.\dfrac{36}{14}\)

\(=\dfrac{5}{21}-\dfrac{2}{3}\)

\(=\dfrac{-3}{7}\)

d) \(70,5-528:\dfrac{15}{2}\)

\(=70,5-\dfrac{352}{5}\)

\(=\dfrac{1}{10}\)

C1: Bình phương 2 vế ta có: \(55-6\sqrt{6}=\left(a+b\sqrt{6}\right)^2\)

<=> \(55-6\sqrt{6}=a^2 +6b^2+2ab\sqrt{6}\)

=>  a² + 6b² = 55 và 2ab = - 6

=> a² + 6b² = 55   (1)   và ab = -3  => a = -3/b (2)

thế (2) vào (1) ta được : \(\left(-\frac{3}{b}\right)^2+6b^2=55\) => \(9+6b^4=55b^2\)

=> 6b⁴ - 55b² + 9 = 0 => 6b⁴ - 54b² - b² + 9 =0 <=> 6b².(b² - 9) - (b² - 9) = 0 <=> (6b² - 1).(b² - 9 ) = 0 

<=> b² = 1/6 (Loại; vì b nguyên )  hoặc b² = 9 

+) b² = 9 => a² = 1 => a = 1 hoặc - 1 ; b = 3 hoặc - 3

Do \(a+b\sqrt{6}\) > 0  và a; b trái dấu nên a =  -1; b = 3 => a+ b = 2

Vậy a +  b  = 2

C2: \(\sqrt{55-6\sqrt{6}}=\sqrt{\left(3\sqrt{6}\right)^2-2.3\sqrt{6}.1+1}=\sqrt{\left(3\sqrt{6}-1\right)^2}\)

= \(\left|3\sqrt{6}-1\right|=3\sqrt{6}-1\)

=> a = -1; b = 3 => a + b = 2

\(1^1-1=0\)

\(2^2-1=3\)

\(3^2-1=8\)

\(4^2-1=15\)

\(5^2-1=24\)

Giảm số bị trừ đi 18 đơn vị thì hiệu sẽ giảm 18 đơn vị.

Giảm số trừ đi 95 đơn vị thì hiệu sẽ tăng 95 đơn vị.

Vậy hiệu mới sẽ là:430-18+95=507

Let's see the Ngoc Son Temple

What about seeing the Ngoc Son Temple?

Why don't we see the Ngoc Son Temple?

I. Choose the word whose underlined part is pronounced differently . (2.5pts)

1. C. of

2. A. allow

3. A. cyclist

4. A. wear

5. D. tidy

6. A. telephones

7. A. often

8. D. ceiling

9. B. hour

10. C. this

1. His student (listen)__listen__ to him.

2. What about (play)__playing__ basketballl this afternoon.

3. Let's (take) __take__a break.

4. It (rain)__rains__a lot in this city, but it (not rain) __isn't raining__now.

Dung, let's listen to music

What about listening to music?

Why don't we listen to music?

1. D

2. C

3. C

4. C

5. A

6. B

7. B