bài 18: cho tứ giác abcd không phải là hình thang, ab và cd cắt nhau tại e, ad và bc cắt nhau tại f. gọi i,j,k lần lượt là trung điểm của các đoạn thẳng ac, bd và ef. chứng minh i,j,k thẳng hàng.

Khử hoàn toàn 32g hỗn hợp Oxit gồm CuO và 1 oxit sắt bằng khí Hiđro ở nhiệt độ cao. Sau p/ứng thu được hỗn hợp chất rắn, cho hỗn hợp chất rắn này tác dụng hoàn toàn với Axit H₂SO₄ loãng thấy thoát ra 6,72 lít khí ở ĐKTC và 6,4 chất rắn.

a. Tìm CTHH của OXIT Sắt đó

b. Tính thành phần % theo KL của mỗi OXIT trong Hỗn hợp ban đầu

giup mk di

Rewrite the following sentences, using phrase of purpose.

1. Leave aerly so that you may get home before dark.

=> You should leave early in order to get home before dark.

2. This man changed his address constantly so that he could void the police.

=> This man changed his address constantly to avoid the police.

3. I shouted in order that I cuold warn everyone of danger.

=> I shouted so as to warn everyone of danger.

4. Banks are developed so that they can keep people's money safe.

=> Banks are developed in order to keep people's money safe.

5. Mary went to the library in order to that she could borrow some books.

=> Mary went to the library so as to borrow some books.

6. Yesterday father went to the bank so that he would open a checking account.

=> Yesterday father went to the bank in order to open a checking account.

7. I went to see him so that I could find out what had happened.

=> I went to see him so as to find out what had happened.

8. Tom is saving up so that he can buy a new bicycle.

=> Tom is saving up so as to buy a new bicycle.

9. He hurried so that he could catch the train.

=> He hurried so as to catch the train.

10. She is learning French so that she will be able to speak it when she comes to Paris.

=> She is learning French so as to speak it when she comes to Paris.