\(\dfrac{x}{27}=\dfrac{2}{9}-\dfrac{1}{3}\Rightarrow\dfrac{x}{27}=-\dfrac{1}{9}\Rightarrow\dfrac{x}{27}=\dfrac{-3}{27}\Rightarrow x=27\)

\(\dfrac{x}{27}=\dfrac{2}{9}-\dfrac{1}{3}=-\dfrac{1}{9}\Rightarrow x=-\dfrac{1}{9}.27=-3\).

a: Xét tứ giác ABDC có

M là trung điểm của BC

M là trung điểm của AD

Do đó: ABDC là hình bình hành

mà \(\widehat{BAC}=90^0\)

nên ABDC là hình chữ nhật

Mình chưa thấy câu hỏi bạn ạ!

hong câu hỏi sao giải 

I.

1C 2B 3C 4B

II.

5C 6C 7C 8A 9D 10A 11C 12D 13A 14C 15A 16B 17B 18B 19C 20A 

III.

21B 22A 23A 24C

IV.

25. On the second Sunday in May.

26. No, they aren't.

27. Greeting cards, gifts, a day of leisure, breakfast cooked by their families and served to them on a tray in bed and a plant.

28. In a restaurant or in one of their home.

29. Greeting cards and gifts.

V.

30. I wish I remembered her surname.

31. This popular TV program is watched by millions of people every week.

32. I suggest putting garbage bins around the schoolyard.

33. Not as many people smoke as they used to.

34. Although I tried to stop smoking, it was very difficult to do.

35. I was such a smoky bar that we left it.

VI.

35. Don't press the red button in any circumstances.

36. Although he was tired, he agreed to play tennis.

37. She finds it easy to study maths.

38. I will inform you immediately when I go home.

39. It wass nobody's fauly that the meeting was cancelled.

40. The gate was closed to stop children from running into the road.

VII.

41C 42A 43D 44D 45A 46B 47C 48B 49A 50C

Lời giải:

Đặt \(\sqrt[3]{5\sqrt{2}+7}=m; \sqrt[3]{5\sqrt{2}-7}=n\)

\(m^3-n^3=14\)

\(mn=1\)

\((a+b+c)^3=(m-n)^3=m^3-3mn(m-n)-n^3=14-3(m-n)\)

\(\Leftrightarrow (a+b+c)^3=14-3(a+b+c)\)

\(\Leftrightarrow (a+b+c)^3+3(a+b+c)-14=0\)

\(\Leftrightarrow (a+b+c)^2[(a+b+c)-2]+2(a+b+c)(a+b+c-2)+7(a+b+c-2)=0\)

\(\Leftrightarrow (a+b+c-2)[(a+b+c)^2+2(a+b+c)+7]=0\)

Dễ thấy biểu thức trong ngoặc vuông $>0$ nên $a+b+c-2=0$

$\Leftrightarrow a+b+c=2$

$ab+bc+ac=\frac{(a+b+c)^2-(a^2+b^2+c^2)}{2}=\frac{2^2-1}{2}=\frac{3}{2}$

caused

imbalances 

diet

nutritionist 

healthy 

energy 

carbohydrates

result

important 

blood 

absorb

maintain 

5:

a: Xét ΔABD vuông tại D và ΔACE vuông tại E có

góc A chung

=>ΔABD đồng dạng với ΔACE

b; ΔABD đồng dạng với ΔACE

=>AD/AE=AB/AC

=>AD/AB=AE/AC

Xét ΔADE và ΔABC có

AD/AB=AE/AC

góc DAE chung

=>ΔADE đồng dạng với ΔABC

c: ΔADE đồng dạng với ΔABC

=>S ADE/S ABC=(AD/AB)^2=1/4