\(\left(x-2\right)\left(x+2\right)\left(x^2-10\right)=72\)

\(\Leftrightarrow\)  \(\left(x^2-4\right)\left(x^2-10\right)=72\)  \(\left(\text{*}\right)\)

Đặt  \(y=x^2-7\)  \(\left(\text{**}\right)\), khi đó, pt  \(\left(\text{*}\right)\)  trở thành, 

\(\left(y+3\right)\left(y-3\right)=72\)

\(\Leftrightarrow\)  \(y^2-9=72\)

\(\Leftrightarrow\)  \(y^2=\text{81}\)  

\(\Leftrightarrow\)  \(y=9\)  hoặc  \(y=-9\)

\(\text{*)}\)  Với trường hợp  \(y=9\)  thì khi đó,  \(x^2-7=9\)  \(\Leftrightarrow\)  \(x^2=16\)  \(\Leftrightarrow\)  \(^{x=4}_{x=-4}\)

\(\text{*)}\)  Với trường hợp  \(y=-9\)  thì  từ  \(\left(\text{**}\right)\)  suy ra  \(x^2-7=-9\)  \(\Leftrightarrow\)  \(x^2=-2\)  (vô nghiệm do  \(x^2\ge0\)  với mọi  \(x\))

Vậy, tập nghiệm của pt là  \(S=\left\{-4;4\right\}\)

Viết lại câu sao cho nghĩa không đổi:

1. She isn't old enough to be in my class.

(so...... that)

(too)

2. They aren't tall enough to reach the fan.

(too)

(such ...that)

3. The coat isn't thick enough for you to wear on cold winter days.

(too)

(such ..... that)

4. The room was too small for six of us to live in.

(enough)

(such... that)

5. The exercises weren't easy enough for us to do in 15 minu8tes.

(such ...that)

(so...that)

là vết chặt nha bạn

hihihi

Viết lại câu sao cho nghĩa không đổi:

1. The bags were too heavy for him to lift. (So......that) (such..... that) 2 cách

2. Seh is intelligent enough become Miss World. ( such ..... that)

3. The weather was fine enough for us to go camping. ( such......that)

4. Those apples are too green for us to eat.(enough)

5. The worker is so clever that he can make fine things from wood. (enough)

6. I'm not strong enough to lift it.(so.....that)

7.The exercises were easy enough for us to do in 10 minutes.(such...that)

8. They got up so late that they missed the train. (Enough)

9. The teacher spoke too quickly for us to understand. ( so...that) (enough)

10. These shoes are too small for her to wear. (So...that) (such...that)