Bài 2

a) Nếu một đường thẳng vuông góc với một trong hai đường thẳng song song thì nó cũng vuông góc với đường thẳng kia.

b) Xem hình vẽ:

.

 Bài 4: 

Nếu hai đường thẳng cùng vuông góc với đường thẳng thứ 3 thì hai đường thẳng đó song song với nhau:

GT: a vuông góc với c, b vuông góc với c

KL: a song song với b

Bài 3 chịu

Tham khảo:

Tet, also known as Lunar new year festival, is the biggest traditional festival in Viet Nam. Tet is usually from the end of January to early February. Before Tet, Vietnamese prepare many things for the three main days. They clean their house and decorate with flowers such as kumquat tree or peach blossom. A huge amount of food will be bought before Tet for making traditional dishes. Banh Chung, Banh Tet, Gio cha, Xoi and Mut, …and candies are the foods that must have on Tet holidays. During Tet, people visit their relatives’ homes and give wishes. However, the Vietnamese believe that the first visitor a family receives in the year determines their fortune for the entire year, people never enter any house on the first day without being invited first. Another custom is giving lucky money, which is put into a red envelope as a symbol of luck and wish for a new age. Traditionally, elders will give lucky money to children and the oldest people in the family. However, nowadays, people can give it to anyone including friends, parents, neighbors,… Besides, Vietnamese usually go to pagodas or temples to pray for health, wealth, success,… To Vietnamese, Tet is the happiest time of all year around, members in a family can gather together, which is a meaningful messages of Lunar New year festival. All in all, Tet is all about back to origins, be good to others, enjoy the precious moment, and wish for the best to come.

In the eyes of foreigners, Vietnamese people is famous for their friendliness, courage, hardworkingness, hospitality and many things which are concerning economic diplomacy. But when the bad time comes, there's a traditional has helped Vietnam put throughout all the difficulties since Hung Vuong regime. It is solidarity, it always rises among people when bad circumstances happen such as the Covid-19 incident in these days. This is the traditional characteristic of Vietnamese people that I love the most. As the saying goes, who weathers the storm isn't harmed during a difficult period. In 2020, Vietnam was said to be the Asian Miracle - one of four countries that have lowest death rates. Not only thanks to government's rapid isolation of outbreaks (Directive No.16), but also thanks to people's solidarity and voluntary compliance with the new Directive.

Phương trình hóa học của phản ứng:

a) 2HgO → 2Hg + O2.

Số phân tử HgO : số nguyên tử Hg : số phân tử O2 là 2 : 2 :1.

2Fe(OH)3 → Fe2O3 + 3H2O.

Số phân tử Fe(OH)3 : số phân tử Fe2O3 : số phân tử H2O là 2 : 1 : 3.

Bài tập 2:

a, Chao ôi, chiếc áo này đẹp quá!

b, Trời ơi, lâu lắm mới gặp lại bạn!

c, Ôi không, mình lỡ làm rơi chiếc cốc này rồi!

Bài tập 1: 

a, Bạn hãy cho mình mượn cuốn truyện này nhé!

b, Chị ơi, phền chị lấy hộ em cốc nước nhé.!

c, Bố mẹ ơi, con đi chơi với bạn một lát nhé!

E cảm ơn cô ạ

Có thời gian viết cái này chắc bạn có đủ thời gian viết đủ bài này r nhỉ :)))

bài nào bạn , phần câu hỏi hả ??

Nguyên tử cacbon có số lớp electron như nguyên tử nitơ và nguyên tử neon. (2 lớp e)