Giải thích các bước giải:

A =1/2.5 + 1/5.8 + 1/8.11 + … +1/92.95 + 1/95.98

=1/3 . (1/2-1/5+1/5-1/8+1/8-1/11+…+1/92-1/95+1/95-1/98)

=1/3 . (1/2 – 1/98 )

=1/3 . 24/49

=8/49`

vậy `A=8/49`

A

{-1; 2}

1. D

2. A

3. A

4. B

5. D

6. C

Quần áo mùa hè thường được may bằng vải sợi bông, sợi lanh, sợi tơ tằm vì: Loại vải này có đặc điểm là thoáng mát, thấm hút mồ hôi, giữ nhiệt tốt, an toàn và thân thiện với môi trường.

D

I. Rearrange the sentences using the following words:

1. the/ Sydney/ city/ cleanest/ is /the/ world. / in/

=>The Sydney city is the cleanest in the world.

2. went/ I/ to/ yesterday. / school/ by/ bike/

=> I went to school by bike yesterday

3. must/ We/ every day. / wear/ our/ at/ uniforms/ school/

=>We must wear our uniforms at school everyday.

4. learning/ They/ are/ now. / English/

=>They are learning Engish now.

5. to/ What/ would/ drink? / you/ like/

=>What would you like to drink?

II. Complete the second sentence so that it means the same as the sentence before:

1. The weather was bad, so we postponed the trip

=>We postponed the trip because the weather was bad.

2. We do a lot of activities in this summer.

=>We take part in a lot of activites in this summer.

3. The Me Kong River is longer than the Red River.

=>The Red River is shorter than The Me kong river.

4. It is wrong of us to throw rubbish.

=> We mustn’t throw rubbish. 

5. Hoa is the best at English in her class

=>Nobody in Hoa’s class is better than her.

cultural

1. x=2, y=1

2. x=2, y=-2

3. x=3/2, y=1

4. x=-5/6, y=1/4

5. x=2/3, y=11/3

1.B 2.C 3.D