1B

2C

3C

4C

5D

6C

7D

12B

13B

14C

15D

16A

17C

18D

19C

20D

21C

22C

23D

a: \(\Leftrightarrow\left\{{}\begin{matrix}3x+6y=4\\x+4y=2\end{matrix}\right.\Leftrightarrow\left\{{}\begin{matrix}y=\dfrac{1}{3}\\x=\dfrac{2}{3}\end{matrix}\right.\)

Lời giải:

a. ĐKXĐ: $x^2+5x+4\neq 0$

$\Leftrightarrow (x+1)(x+4)\neq 0$

$\Leftrightarrow x\neq -1; x\neq -4$

b. $M=\frac{x^2+4x+3}{x^2+5x+4}=\frac{(x+1)(x+3)}{(x+1)(x+4)}=\frac{x+3}{x+4}$

Tại $x=0$ thì $M=\frac{0+3}{0+4}=\frac{3}{4}$

Tại $x=2$ thì $M=\frac{2+3}{2+4}=\frac{5}{6}$

Tại $x=-3$ thì $M=\frac{-3+3}{-3+4}=0$

1. ∅

2. a

3. ∅

4. the

5. an

6. the/∅

7. ∅

8. ∅

9. the

10. ∅

1 0

2 a

3 0

4 the

5 an

6 the

7 0

8 0

9 0

10 0

a, Vì AC⊥AB và BD⊥AB nên AC//BD

b, Vì AC//BD nên \(\widehat{D_1}=\widehat{ACD}\) (so le trong)

Mà \(\widehat{ACD}+\widehat{C_1}=180^0\left(kề.bù\right)\Rightarrow\widehat{ACD}=\widehat{D_1}=180^0-70^0=110^0\)

2 True

3 False

4 True

5 False

b

1 It is located on top of a hill

2 They were used to protect people inside the castle

3 They can go upstairs on narrow staircases

4 15000 people visit the castle each day