a: xét ΔABC có \(\hat{ABC}+\hat{ACB}+\hat{BAC}=180^0\)

=>\(\hat{ACB}=180^0-80^0-50^0=50^0\)

TA có; \(\hat{xAC}+\hat{BAC}=180^0\) (hai góc kề bù)

=>\(\hat{xAC}=180^0-80^0=100^0\)

Ay là phân giác của góc xAC

=>\(\hat{xAy}=\hat{yAC}=\frac12\cdot\hat{xAC}=\frac12\cdot100^0=50^0\)

Ta có: \(\hat{yAC}=\hat{ACB}\left(=50^0\right)\)

mà hai góc này là hai góc ở vị trí so le trong

nên Ay//BC

b: CE//AB

=>\(\hat{ACE}=\hat{BAC}\) (hai góc so le trong)

=>\(\hat{ACE}=80^0\)

XétΔCAE có \(\hat{ACE}+\hat{CAE}+\hat{CEA}=180^0\)

=>\(\hat{CEA}=180^0-80^0-50^0=50^0\)

c: Ta có; AD⊥ a

BC⊥ a

Do đó: AD//BC

mà AE//BC

và AD,AE có điểm chung là A

nên D,A,E thẳng hàng

f(1)=3

f(-1)=3

\(\text{f(1)=}2.1^2+1=3\)

\(\text{f(-1)=}2.\left(-1\right)^2+1=3\)

\(\text{f(2)=}2.2^2+1=9\)

\(\text{f(0)=}2.0^2+1=1\)

\(\text{f(-3)=}=2.\left(-3\right)^2+1=19\)

1 old enough to get married

2 was too hot for me to drink

3 good enough for them to go for a walk

4 is so hard that he asks his friend for some help

5 an easy question that he can answer it

6 is a lot of information on the newspapers

7 should buy the furniture online to save time

8 Sue left the house, she had checked that she had lost her key

9 Mark was parking his car, he noticed the tire was flat

10 Kate had take 2 aspirins, she felt a lot better

6. a 

7. c

8. c

9.b

10.a

III.

1. difference

2.fishing

3.succes

4.entertainment

5.volutest : cau nay minh ko chac

IV:

1. d

2.b 

3.a

4.c

5. a

V:

1. tet is national and family festival

2.từ at tet đến for tet , at home từ at home cho đến the air

3. chilren are given a lucky money warpped in red envelopes

4.happy hallowen 

VI:

V:

1. in one of her books they are given linda a prize 

mấy câu này mình cx ko chắc nx

B

B