VP `=2sin (3x)/2 . cos (3x)/2`

`=sin (2. (3x)/2)`

`=sin3x=` VT.

`(sin2a=2sinacosa)`

What do you need to improve ?

110 C thì đúng rồi nhưng 111 là B chứ nhỉ ?

5. The hospital is to the right of the bookstore.
1. There isn't any umbrella in my bag.
2. There are a table, a chair, an air conditioner in my room.
3. The book is on the pen.
4. The fan is in front of the cat.
5. He likes studying English the most.

`A=x^2+8x+10`

`=x^2+2.x.4+4^2-6`

`=(x+4)^2-6`

Có: `(x+4)^2 >=0 forall x => (x+4)^2-6 >=-6`

`=> A_(min)=-6 <=> x=-4`.

ĐK: $\begin{cases}x^2-2x≥0\\2-x≥0\\\end{cases}$ `<=>` $\begin{cases}x≤0 \vee x ≥2\\x≤2\\\end{cases}$ ` <=> ` $\begin{cases}x≤0\\x=2\\\end{cases}$

`\sqrt(x^2-2x)=2-x`

`<=>x^2-2x=(x-2)^2`

`<=>x^2-2x=x^2-4x+4`

`<=>-2x=-4x+4`

`<=>x=2`

Vậy `S={2}`.