Tiên đề Ơ-clít: Qua một điểm ở ngoài một đường thẳng, chỉ có một đường thẳng song song với đường thẳng đó.

- Dảk mỗi đoạn đấy thôi, đoạn sau hết dảk rồi. :v

Two years ago, I went to Sam Son beach with my family. It was a beautiful day with sunshine everywhere. When I went swimming, suddenly, the cloud became dảk, the wind blew so roughly, the waves were higher than usual. I anxiously backed to the seaside with my parents. Then, we were back to the hotel. At the hotel, my cousin with I played extremely fun card games. I won a lot of money. It was an unforgettable holiday. <3

`(x-1)/4=(-9)/(1-x)`

`(x-1)(1-x)=-9.4`

`(x-1)(x-1)=36`

`(x-1)(x-1)=6.6=(-6).(-6)`

`[(x-1=6),(x-1=-6):}`

`[(x=7),(x=-5):}`

a) `(1/5x-4/5)((2x-1)/3-2/6)=0`

`[(1/5 x-4/5=0),(2/3 x -1/3 -1/3=0):}`

`[(x=4),(x=1):}`

.

c) `50% x+2/3 x=x-5`
`1/2 x+2/3 x= x-5`
`(1/2+2/3-1)x=-5`
`1/6 x=-5`
`x=-30`
.
`A=3/(3.5)+3/(5.7)+....+3/(97.99)`
`=> 2/3 A = 2/(3.5)+2/(5.7)+....+2/(97.99)`
`=1/3-1/5+1/5-1/7+...+1/97-1/99`
`=1/3-1/99`
`=32/99`
`=> A=16/33`

Có: `M` là trung điểm của `AB`.

       `N` là trung điểm `AC`.

`=> MN` là đường trung bình của \(\triangle\)`ABC`

`=> MN////BC`

`=> MNBC` là hình thang.

    \(x_2=x_1^2\Leftrightarrow2-m=\left(2+m\right)^2\Leftrightarrow\left[{}\begin{matrix}m=\dfrac{-5+\sqrt{17}}{2}\left(L\right)\\m=\dfrac{-5-\sqrt{17}}{2}\left(L\right)\end{matrix}\right.\)

`(2x-y^3)-2(4x^3+1)+6(2x-y)+y^3`

`=2x-y^3-8x^3-2+12x-6y+y^3`

`=(y^3-y^3)-8x^3+(2x+12x)-6y-2`

`=-8x^3+14x-6y-2`