a) khí oxi dc điều chế do nhiệt phân 1 mol \(KClO_3\) thì thu dc 43.2 g khí oxy. tính hiệu suất phản ứng?

b) Cho lượng khí oxi vừa điều chế dc để đốt cháy hoàn toàn phot pho với H= 98%. tính lượng phốt pho đã đốt cháy?

cho tam giác ABC vuông tại A, đường cao BH

a) CM: tam giác ABC\(\sim\) tam giác AHB. suy ra \(AB^2=AH.AC\)

b) CM: \(BC^2=AC.HC\)

c) cho biết AB=20 cm, BC= 15 cm. tính AH

REWRITE THE FOLLOWING SENTENCES WITHOUT CHANGING THEIR MEANINGS

1 Would you please turn of the light?

-> Would you mind...........................

2 Engish is proken all over the world.

-> People..................................................

3 She is a very good singer

-> She sings......................................................

4. The doctor said to her, " Stay in bed"

-> The doctor told her..............................................

5. Her dress is not as long as yours.

-> Your dress is................................

Rewrite the sentences as directed

1 He is called a tractor driver. ( WE CALL........)

.............................................................................

2 The kitchen is being cleaned. ( SOMEONE.......)

................................................................................

There is one mistake in each sentence. Find and correct it.

1 When will the gift bring here?

2 It's difficult to building a house in one month.

3 I'm afraid the meal isn't prepare well enough for the party

4 She was happy that her old friend remembering her birthday

5 It's ineasy for prevent people from pokkuting the environment

6 Will be this school upgraded ext year?

7 Every milk bottle can is reused thirty times

8. Don't throw these things away

9 Garbage should be used to make fertilize.

10 The government call people for their saving natural resource.

Rewrite the following sentences without changing their meanings

1. To study Vietnamese is nots difficult

-> It.................................................

2 that you can stay whith us this weekend is wonderful

-> It ................................................................................

3. Please send me a postcard.

-> Will you..........................................................

4 Did you open that box?

-> Was.........................................

5. Peter was tired, so he went to bed early.

-> Because.............................................

Give the correct form ò the words in brackets

1 his land is.................( fertilizer)

2. on the map, blue ......................water

3. what is the..........this water on the floor (explain)

4. this...........is tin ( mix)

viết một đoạn văn ngắn từ 7- 10 câu, chủ đề tự chọ có sử dụng biện phâp tu từ nói giảm nói tránh. Gạch chân biện pháp tu từ nói giảm nói tránh và cho biết tác dụng của nó

complete the passages with the Present perfect or the Simple past of the verbs in bracket

A. At 4 p.m my neighbor ( 1.ring)..............up and (2.say)........," Is Tom with you ?" Tom, her son, ( 3. spend)..............most ò hí time in my garden playing with my children, si whenever she (4. not be able)................. to find him she (5. ring)..............me."I'm afraid I ( 6.not see )...........him today," I ( 7. say)............." But my children (8.go)..............to the beach this morning and (9. not come)................ back yet. Perhaps he (10. go)...............with them"

B. When I (1. buy)..............my new house I (2.ask ).............for a telephone. The Post Office (3. tell)................me to wait, but I (4. wait).............. a year now and my phone still ( 5. not come)..................

Ta có: A = 3 + 3² + 3³ + ... + 3¹⁰⁰

=> 3A =  3² + 3³ + 3⁴ + ... + 3¹⁰¹

=> 3A - A = 3¹⁰¹ - 3

=> 2A = 3¹⁰¹ - 3

=> 2A + 3 = 3¹⁰¹

=> x = 101