+Giai đoạn 1: Xuất hiện thực vật ở nước.
+Giai đoạn 2: Các thực vật ở cạn lần lượt xuất hiện.
+Giai đoạn 3: Sự xuất hiện và chiếm ưu thế của hạt kín.

2)a)3x(x-5)-(x-1)(2+3x)=30

<=>3x²-15x-3x²+x+2=30

<=>-14x+2=30

<=>-14x=30-2

<=>-14x=28

<=>x=-2

b)(x+2)(x+3)-(x-2)(x+5)=0

<=>x²+5x+6-x²-3x+10=0

<=>2x+16=0

<=>2x=-16

<=>x=-8

c)(3x+2)(2x+9)-(x+2)(6x+1)=9

<=>6x²+31x+18-6x²-13x-2=9

<=>18x+16=9

<=>18x=9-16

<=>18x=-7

<=>x=-7/18

Hello my name is Golden Darkness. Today, I would like to introduce about my neighborhood. My neighborhood is in Tan Thanh province. It is noisy but it is clean and convenient. There are Shops, Schools, Restaurants, hotels, market and so on. The streets are busy and crowded during the day. I like restaurants best because the food are very good. The people here are very friendly and kind. I like living here so much because every thing I need is only five minutes away.Thanks for listening to me

Tổng 2 số đó là:  186 x 2 = 372

Số bé là:  372 : (2+1) x 1 = 124

Số lớn là:  124 x 2 = 248

Đs:...

Video games are children’s ever favourite time pass. Not only the kids, but many adults do enjoy playing these.

It is a wide spread mind-set that video games are a bad habit amongst the kids which damages their vision. Though not completely incorrect, still we can’t quote that video games are only hazardeus without any good features to project to.

If we count on its bad effects, it definitely decreases the eye-sight. It is addiction forming as well. People tend to skip their duties in this addiction. Children hardly prefer to go out to play, thus lacking the physical activities.

Going on to the positive impacts of the video games, it increases the reflexes in the individual. The person playing video games on a regular basis can react to a stimulus in a much faster and sharp manner in comparison to others.

Video games are undoubtedly good mode for entertainment. It helps to keep the kids within home, especially in the summer vacation time, avoiding the exposure to hot sun.

Neu la Van HSG, chi co dan y dua vao viet thoi bn nhe!^^

Ta có : 

3 = 0 x 15 + 3

18 = 1 x 15 + 3

48 = 2 x 15 + 18 = 2 x 15 + 1 x 15 + 3

93 = 3 x 15 + 48 = 3 x 15 + 2 x 15 + 1 x 15 + 3

153 = 4 x 15 + 93 = 4 x 15 + 3 x 15 + 2 x 15 + 1 x 15 + 3

Số thứ 100 là : 99 x 15 + 98 x 15 + ... + 1 x 15 + 3

= 15 x ( 99 + 98 + .... + 1 ) + 3

= 15 x [ ( 99 - 1 ) : 1 + 1 x  ) + 3 

= 15 x  [ ( 99 + 1 ) x 99 : 2 ] + 3

= 15 x 4550 + 3

= 68253