III. Write a/an or the if necessary. (Điền mạo từ a/an/the / zero article) 1 Who is …………best player on your team? 2 I don't watch ………… TV very often. 3 "Is there ………… bank near here?"-"Yes, at ………… end of this block." 4 I can't ride. ............. horse. 5 ………… sky is very clear tonight. 6 Do you live here, or are you …………tourist? 7 What did you have for ………… lunch? 8 Who was …………first president of ………… United States? 9 I'm not feeling very well. I have………… headache. 10 I’m sorry, but I've forgotten your name. I can never remember………… names. 11 What time is …………next train to Boston? 12 Kate rarely sends …………emails. She prefers to call people. 13 "Where's Sue?"-"She's in.................backyard." 14 Excuse me, I'm looking for …………Majestic Hotel. Is it near here? 15 Kevin was sick ………… last week, so he didn't go to …………work. 16 Everest is................. highest mountain in world. 17 I usually listen to …………radio while I'm having …………breakfast. 18 I like sports. My favorite sport is …………basketball. 19 Julia is ………doctor. Her husband is………… art teacher. 20 My apartment is on …………second floor. Turn left at …………top of …………stairs, and it's on…………right. 21 After …………dinner, we watched …………TV. 22 I've been to …………northern Mexico but not to ………… south
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Bạn nên gõ đề bằng công thức toán (biểu tượng $\sum$ góc trái khung soạn thảo) để mọi người hiểu đề của bạn hơn.
a) ĐKXĐ: x\(\ne\)0, x\(\ne\)2
Ta có:
A= 2x-4/ x2- 2x = 2(x-2)/ x(x-2) = 2/x
Vậy...
b) Ta thấy x=26 thỏa mãn ĐKXĐ
Thay x=26 vào bt A ta được
A= 2/26 = 1/13
Vậy....
c) Với x\(\ne\)0, x\(\ne\)2 ta có A=12 \(\Leftrightarrow\) 2/x =12 \(\Leftrightarrow\) x=1/6
Vậy....
\(x^2\) - 8\(x\) + 19
= (\(x^2\) -2.\(x\) . 4 + 42) + 3
= (\(x\) - 4)2 + 3
Vì (\(x\) - 4)2 ≥ 0 ∀ \(x\) ⇒ (\(x\) - 4)2 + 3 ≥ 3 dấu bằng xảy ra khi
\(x\) - 4 = 0 ⇒ \(x\) = 4
Vậy giá trị nhỏ nhất của \(x^2\) - 8\(x\) + 19 là 3 xảy ra .khi \(x\) = 4
Q = x^2 + 8x + 20
= (x^2 + 8x + 16) + 4
= (x+4)^2 + 4 ≥ 4 với mọi x
Dấu = xảy ra khi :
x+4=0 hay x = -4
VẬY MIN Q = 4 tại x = -4
Q = x2+ 8x + 20
= x2+ 2.4.x + 16+ 4
= (x+4)2+4
Vì (x+4)2 \(\ge\) 0 với mọi x \(\Rightarrow\) (x+4)2+ 4\(\ge\) 0+4
hay Q\(\ge\) 4
Dấu "=" xảy ra \(\Leftrightarrow\) (x+4)2=0 \(\Leftrightarrow\) x+4=0 \(\Leftrightarrow\) x= -4
Vậy Q đạt giá trị nhỏ nhất khi x= -4
a, Ta có: \(n_{Na}=\dfrac{2,3}{23}=0,1\left(mol\right)\)
\(m_{HCl}=60.7,3\%=4,38\left(g\right)\Rightarrow n_{HCl}=\dfrac{4,38}{36,5}=0,12\left(mol\right)\)
PT: \(2Na+2HCl\rightarrow2NaCl+H_2\)
Xét tỉ lệ: \(\dfrac{0,1}{2}< \dfrac{0,12}{2}\), ta được HCl dư.
Theo PT: \(n_{H_2}=\dfrac{1}{2}n_{Na}=0,05\left(mol\right)\Rightarrow V_{H_2}=0,05.24,79=1,2395\left(l\right)\)
b, \(n_{HCl\left(pư\right)}=n_{NaCl}=n_{Na}=0,1\left(mol\right)\)
\(\Rightarrow n_{HCl\left(dư\right)}=0,12-0,1=0,02\left(mol\right)\)
Ta có: m dd sau pư = 2,3 + 60 - 0,05.2 = 62,2 (g)
\(\Rightarrow\left\{{}\begin{matrix}C\%_{NaCl}=\dfrac{0,1.58,5}{62,2}.100\%\approx9,41\%\\C\%_{HCl}=\dfrac{0,02.36,5}{62,2}.100\%\approx1,17\%\end{matrix}\right.\)
1 June is not as hot as July
2 Although it was a comedy, most audience fell asleep
3 When they got divorced, they were married for five years
4 John was very sad because he failed the final exam
1 Cấu trúc so sánh ngang bằng: S1 + be as + adj + as S2
3 When sẽ đưa vào cùng với mệnh đề có hành động xen vào
1 the
2 0
3 a - the
4 a
5 the
6 a
7 0
8 the - the
9 a
10 0
11 the
12 0
13 the
14 the
15 0 - 0
16 the
17 the - 0
18 0
19 a - an
20 the - the - the - the
21 0 - 0
22 the - the