Khi chỉ còn lại phép cộng và phép trừ 

Gọi x (km) là quãng đường AB (x>0)

-Thời gian đi của người thứ 1 là: 8h-6h=2h

-Thời giân đi của người thứ 2 là: 2h-40'=8/3h

-Vận tốc đi của người thứ 1 là: x/2 (km/h)

-Vận tốc đi của người thứ 2 là: 3x/8 (km/h)

Vì người thứu 2 đi với vận tốc chậm hơn người thứ 1 10km/h nên ta có pt:

x/2 - 3x/8 = 10

⇔ 8x/16 - 6x/16 = 160/16

⇔ 8x - 6x = 160

⇔ 2x = 160

⇔ x = 80 (nhận)

Vậy quãng đường AB dài 80km

Trong phân bào lần II của giảm phân, NST kép xếp thành một hàng ở mặt phẳng xích đạo của thoi phân bào ở kì nào?

A. Kì sau

B. Kì giữa

C. Kì đầu

D. Kì cuối

a. -3x^2+7x+10=0

⇔ 3x^2-7x-10=0

⇔ 3x^2+3x-10x-10=0

⇔ 3x(x+1)-10(x+1)=0

⇔ (3x-10)(x+1)=0

⇔ 3x-10=0 hoặc x+1=0

⇔ x=10/3 hặc x=-1

x^4-2x^3+4x^2-3x+2=0

⇔ x^4-2x^3+x^2+3x^2-3x+2=0

⇔ (x^4-2x^3+x^2) + 3(x^2-x+1/4) + 5/4=0

⇔ (x^2-x)^2 + 3(x-1/2)^2 + 5/4=0
(vì (x^2-x)^2 ≥ 0 với mọi x

⇒ (x^2-x)^2 + 3(x-1/2)^2 + 5/4 > 0 với mọi x

⇒ Phương trinh trên vô nghiệm

You ought to limit eating candy

*Acivities at school

This is my school, It's beautiful and large. My school has many trees and the stadiums for children to play. There are 48 classes, one thousand students and one hundred teacher. At school, I learn 14 subject are: Literature, Math, English, History, Geography, Physics, Biology, Art, Music, Technology, Computer Science, Civil Education, Physical Education. Teachers are teach very well and students are good. At recess, my school has a lot of activities: talking with friends, skipping rope,.... And I love my school very much.
* Acivities after school

After one day in my school, I go home. First, I dressing. then I help my mom with the household and cooking for dinner. When I finished home work, I'm go out playing with my friends. We play chess, soccer, and I like playing badminton. In the evening, after the dinner, I do my homework. Finally, I drink milk and go to bed.

*Your trip to somewwhere

In summer last year, my family visit my grandmother in the countryside. It's about 150km from the Phan Thiet city. Along the side of the road has many trees and the beach very cool. Grandmother's countryside very peace and calm. It's covered by green paddy fields. In the country, I like to get rid of the sorrows. I love living in this country very much.

*About your house

I live in a small house in village. There are four people in my family. There is garden in front of the house. In my house, it's has five room: one livingroom, two bedroom, one kitchen, one bathroom and one tollet. In my livingroom, it's has a television, a salon, a hammock,... In my bedroom, it's has a bed, a pink desk, a wardrobe, a laptop and the fan. In my kitchen, it's has a electric stove, a cooker, a cupboard, a sink, a oven and the dinner table. In bathroom, it's has a washstand, a bathtub, a towel rack. I love my house very much because it's beautiful and I feel happy when I live in my house.