1 C => hers

2 B => will use

3 D => their

4 A => will be pedaling

5 A => travel

6 C => less

7 D => have they

8 D => than

9 A => worked

10 B => fewer

Câu 15:

Gọi $x_0$ là nghiệm chung của 2 pt thì:
\(\left\{\begin{matrix} x_0^2+ax_0+1=0\\ x_0^2-x_0-a=0\end{matrix}\right.\Rightarrow x_0(a+1)+(a+1)=0\)

\(\Leftrightarrow (x_0+1)(a+1)=0\)

Hiển nhiên $a\neq -1$ để 2 PT không trùng nhau. Do đó $x_0=-1$ là nghiệm chung của 2 PT

Thay vào:

$(-1)^2+a(-1)+1=0$

$\Leftrightarrow 1-a+1=0\Rightarrow a=2$

Đáp án C.

Câu 16:

D sai. Trong tam giác vuông tại $A$ là $ABC$, $\cos (90^0-\widehat{B})=\cos \widehat{C}$ và không có cơ sở để khẳng định $\cos \widehat{C}=\sin \widehat{C}$

Câu 18:

$\pi r^2=36\pi \Rightarrow r^2=36\Rightarrow r=6$ (cm)

Chu vi của hình tròn là:

$2r \pi =2.6\pi =12\pi$ (cm)

Đáp án B.

1 The wheel was invented thousands of years ago

2 Is a statue of Chu Van An being built 

3 Is the Temple of Literature surrounded by 4 busy streets

4 Pencil won't be provided at the test, so please,,...

5 We haven't been taught since the last semester 

6 That experiment is being done by a student teacher

7 Was this dictionary bought 2 weeks ago?

8 I amnot impressed by Alan's knowledge about......

9 A new school is going to be built here next year

10 This computer has been used for 2 years