Xét tam giác ABC có BC vuông góc với ab' và b'c' vuông góc với AB

Suy ra BC//B'C'

ÁP DỤNG ĐỊNH LÝ THALES TA CÓ

AB/AB'=BC/B'C'

Suy ra x/x + h = a/a'

Suy ra a'x = a ×( a + h)

Suy ra a'x - ax = h

Suy ra x ×(a'- a)=ah

Suy ra x = ab / a' - a(điều phải chứng minh)

1:

The Muong earn a living by farming and raising animals.

2:

They are in a habit of exercising after work.

1;

if you don't drink more water,you will get more acne.

2:

My sister wants to go to Sa Pa because she wants to see the terraced fields.

3:

unless he spends time on his phone,he will complete his work.

Answer:Teenagers fell stressed because of peer pressure, too much schoolwork, spending too much time on social media, and even bullying. Peer pressure is another reason, as many teens try hard to fit in with their friends.To reduce stress,we should staying calm and relaxed,talk to teachers about your problem,use smartphones responsibly and avoiding bullies wherever possible.