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I/ Circle the best answer (A, B, C or D) to complete the sentences
9. People of ……………… minorities in Phu Yen celebrate Hoi Mua Festival every March.
A. native B. local C . ethnic D. village
10.A lot of dancers go to Rio de Janeiro to ………..the Rio Carnival .
A. joy B. perform C.attend D. appear
11.It must be amazing ……………..elephants racing.
A.see B. to see C. seeing D. saw
12.Minh used to ……his homework late in the evening .
A. does B. do C. doing D. did
14.I have never felt as ………..as I did when I watched that horror film .
A.terrify B.terrified C.terrifying D.terrible
15.We found the plot of the film …………. .
A.bored B.boring C.interested D.acting
16.People in Cannes take the Cannes Film Festival ………..a very serious way .
A.of B.to C.with D. in
Câu 13 bị lỗi
TK cho mình nha !!! (^-^)
I/ Circle the best answer (A, B, C or D) to complete the sentences
9. People of ……………… minorities in Phu Yen celebrate Hoi Mua Festival every March.
A. native B. local C. ethnic D. village
10.A lot of dancers go to Rio de Janeiro to ………..the Rio Carnival .
A. joy B perform C.attend D. appear
11.It must be amazing ……………..elephants racing.
A.see B. to see C. seeing D. saw
12.Minh used to ……his homework late in the evening .
Adoes B. do C. doing D. did
13. The biggest prize of the Cannes Film Festival is the palme d’Or, which is given ……. the best film
A.of B.to C. with D. for
14.I have never felt as ………..as I did when I watched that horror film .
A.terrify B.terrified C.terrifying D.terrible
15.We found the plot of the film …………. .
A.bored B.boring C.interested D.acting
16.People in Cannes take the Cannes Film Festival ………..a very serious way .
A.of B.to C.with D. in
ĐÚNG K
HOK TỐT
\(S=1+2+2^2+...+2^{100}\)
\(2S=2+2^2+2^3+...+2^{100}+2^{101}\)
\(\Rightarrow2S-S=2^{101}-1\)
\(\Rightarrow S=2^{101}-1\)
cho M = \(\frac{a}{a+b+c}+\frac{b}{a+b+d}+\frac{c}{b+c+d}+\frac{d}{a+c+d}\) với a, b, c, d \(\in\)N*
Do a;b;c và d là các số nguyên dương =>
a + b + c < a + b + c + d
a + b + d < a + b + c + d
a + c + d < a + b + c + d
b + c + d < a + b + c + d
=> a/(a + b + c) > a/(a + b + c + d) (1)
b/(a + b + d) > b/(a + b + c + d) (2)
c/(b + c + d) > c/(a + b + c + d) (3)
d/(a + c + d) > d/(a + b + c + d) (4)
Từ (1);(2);(3) và (4)
=> a/(a + b + c) + b/(a + b + d) + c/(b + c + d) + d/(a + c + d) > a/(a + b + c + d) + b/(a + b + c + d) + c/(a + b + c + d) + d/(a + b + c + d)
=> a/(a + b + c) + b/(a + b + d) + c/(b + c + d) + d/(a + c + d) > (a + b + c + d)/(a + b + c + d)
=> a/(a + b + c) + b/(a + b + d) + c/(b + c + d) + d/(a + c + d) > 1
=> M > 1 (*)
Ta có: (a + b + c)(a + d) - a(a + b + c + d)
= a² + ad + ab + bd + ac + cd - (a² + ab + ac + ad)
= a² + ad + ab + bd + ac + cd - a² - ab - ac - ad
= bd + cd
Do a;b;c và d là số nguyên dương
=> bd + cd > 0
=> (a + b + c)(a + d) - a(a + b + c + d) > 0
=> (a + b + c)(a + d) > a(a + b + c + d)
=> (a + d)/(a + b + c + d) > a/(a + b + c) (5)
Chứng minh tương tự ta được:
(b + c)/(a + b + c + d) > b/(a + b + d) (6)
(a + c)/(a + b + c + d) > c/(b + c + d) (7)
(b + d)/(a + b + c + d) > d/(a + c + d) (8)
Cộng vế với vế của (5);(6);(7) và (8) ta được:
(a + d)/(a + b + c + d) + (b + c)/(a + b + c + d) + (a + c)/(a + b + c + d) + (b + d)/(a + b + c + d) > a/(a + b + c) + b/(a + b + d) + c/(b + c + d) + d/(a + c + d)
=> (a + d + b + c + a + c + b + d)/(a + b + c + d) > M
=> 2(a + b + c + d)/(a + b + c + d) > M
=> 2 > M (*)(*)
Từ (*) và (*)(*)
=> 1 < M< 2
=> M không phải là số nguyên
