amazing

My grandfather is too old to work very hard

okiii

I usually sleep for 8 hours

I go to bed quite late, there are days when I just start to sleep

I nap quite a lot, maybe 6 hours a day

I don't usually sleep for a while

Sleep is very important to us, it helps us to grow.

Older people should exercise more to develop their muscles and increase their lifespan.

D

B

A

C

A

wow

Đặt pt tên là (1), pt dưới là(2).

-Có với x>y => VT(1)>VP(1)  (vô lí)

Tương tự với x<y => VT(1)<VP(1)  (vô lí)

=> x=y

(2) <=>  (*)

-Có: 

mà VT18 =>VT=VP=18  <=> x=8

wow