Read the following passage and mark the letter A, B, C, or D on your answer sheet to indicate the correct word or phrase that best fits each of the numbered blanks.

Why read books?

Is it worth reading books, (27)________nowadays there are so many other forms of entertainment?

Some people say that even paperback books are expensive, and not everyone can borrow books from a library. They might add that television is more exciting and that viewers can relax as they watch their favourite (28)_______. All that may be true, but books are still very popular. They encourage the reader to use his or her imagination for a start. You can read a chapter of a book, or just a few pages, and then stop. Of course, it may be so (29)_________that you can't stop! There are many different kinds of books, so you can choose a crime novel or an autobiography, or a book (30)______gives you interesting information. If you find it hard to choose, you can read reviews, or ask friends for ideas. Personally, I can’t do without books, but I can (31)________up television easily enough. You can't watch television at bus stops!

Điền vào ô trống 30

A. whose

B. which

C. what

D. when

hay là dấu ngoặc vuông ý

dấu trị tuyệt đối phải hk bạn

C. BC > AC

Vì \(\widehat{A}>\widehat{B}\) (\(80^0>40^0\))

góc A nào á! góc A lớn là đề cho 90 độ r mà bạn

Anken A (C₄H₈), có đồng phân cis – trans. Vậy A là: 

A. but – 1 – en.

B. but – 2 – en

C. 2 – metylprop – 1 – en

D. 2 – buten

Ok! Giải nhé!

Sửa đề: CM: AD \(\perp\)BC

Xét 2 \(\Delta ABD\) và \(\Delta ACD\), có:

AB = AC (gt)

AD cạnh chung

BD = CD (gt)

\(\Rightarrow\Delta ABD=\Delta ACD\) (c.c.c)

\(\Rightarrow\) \(\widehat{BAD}=\widehat{CAD}\)(2 góc tương ứng)

Gọi I là giao điểm của AD và BC

Xét 2 \(\Delta ABI\) và \(\Delta ACI\), có:

AB = AC (gt)

\(\widehat{BAI}=\widehat{CAI}\)(cmt)

AI cạnh chung

\(\Rightarrow\Delta ABI=\Delta ACI\) (c.g.c)

\(\Rightarrow\widehat{AIB}=\widehat{AIC}\) (2 góc tương ứng)

Mà \(\widehat{AIB}+\widehat{AIC}=180^0\)

\(\Leftrightarrow\widehat{AIB}+\widehat{AIB}=180^0\)

\(\Rightarrow2.\widehat{AIB}=180^0\)

\(\Rightarrow\widehat{AIB}=180^0:2=90^0\)

Vậy \(AI\perp BC\)hay \(AD\perp BC\)(ĐPCM)

bạn đợi mik xí, mik gửi cho bạn mik cái đề kia r mik giải cho nha!

phải là: trên 2 nửa mặt phẳng đối nhau qua AB chớ