1. How long have you lived here ?
2. I wish our holidays weren't too short.
3. In Malaysia, Islam is being practiced by millions of people.
4. Whose pull-over is this ?

`A=(2x)^2+2.2x.1+1^2+1=(2x+1)^2+1`

`=> A_(min)=1 <=>x=-1/2`

`B=(\sqrt2x)^2-2.\sqrt2 x . \sqrt2/2 + (\sqrt2/2)^2 + 1/2`

`=(\sqrt2x-\sqrt2/2)^2+1/2`

`=> B_(min)=1/2 <=> x=1/2`

`C=-(x^2-2.x.3+3^2+6)=-(x-3)^2-6`

`=> C_(max)=-6 <=> x=3`

ĐK: `{(3x+1 >=0),(4+x)>=0):} <=> x>=-1/3`

PT `<=>\sqrt(3x+1)=\sqrt(x+4)+1`

`<=>3x+1=x+4+1+2\sqrt(x+4)`

`<=>2x-4=2\sqrt(x+4)`

`<=>x-2=\sqrt(x+4)`

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

`<=> x^2-5x=0`

`<=>[(x=0(L)),(x=5 (TM)):}`

Vậy `x=5`.

1. My desk has many books.
2. Our garden has money flowers.
3. Nam's family has 4 people.
4. There are 6 hundred students in my school.
5. ARe there 4 people in your family ?

a. Gọi số đo các góc của tứ giác ABCD lần lượt là: `x,2x,3x,4x (x>0)`

Có: `x+2x+3x+4x=360^o` (Tổng 4 góc của 1 tứ giác)

`<=> x=36^o`

`=> \hatA=36^o`

`\hatB=72^o`

`\hatC=108^o`

`\hatD=144^o`

b.

`\hatA+\hatD=180^o`

Mà 2 góc ở vị trí trong cùng phía.

`=> AB ////DC`

`xy.(x-y)=x^2y -xy^2`

Bạn tham khảo: https://hoc24.vn/cau-hoi/biet-ti-so-hai-canh-goc-vuong-cua-mot-tam-giac-vuong-la-3-7-duong-cao-ung-voi-canh-huyen-la-42-cm-tinh-do-dai-hinh-chieu-cua-cac-canh-goc-vuong-tren-canh-huyen-help-me-plz.1283294766368

`\sqrt(3-\sqrt5)+\sqrt(3+\sqrt5) `

`=\sqrt( (6-2\sqrt5)/2) + \sqrt((6+2\sqrt5)/2)`

`=\sqrt( ((\sqrt5)^2 -2.\sqrt5 .1+1^2)/2) + \sqrt(((\sqrt5)^2-2.\sqrt5 .1 +1^2)/2)`

`=\sqrt(((\sqrt5-1)^2)/2) +\sqrt(((\sqrt5+1)^2)/2)`

`= (\sqrt5-1)/2 + (\sqrt5+1)/2`

`=(2\sqrt5)/2=\sqrt5`

Là \(AC=14\sqrt{58}\) ạ.