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

a: \(VP=a^3+b^3+c^3-3bac\)

\(=\left(a+b\right)^3+c^3-3ab\left(a+b\right)-3abc\)

\(=\left(a+b+c\right)\left[\left(a+b\right)^2-c\left(a+b\right)+c^2\right]-3ab\left(a+b+c\right)\)

\(=\left(a+b+c\right)\left(a^2+2ab+b^2-ac-bc+c^2-3ab\right)\)

\(=\left(a+b+c\right)\left(a^2+b^2+c^2-ab-bc-ac\right)=VT\)

b: \(VT=\left(3a+2b-1\right)\left(a+5\right)-2b\left(a-2\right)\)

\(=3a^2+15a+2ab+10b-a-5-2ab+4b\)

\(=3a^2+14a+14b-5\)

\(VP=\left(3a+5\right)\left(a+3\right)+2\left(7b-10\right)\)

\(=3a^2+9a+5a+15+14b-20\)

\(=3a^2+14a+14b-5\)

=>VT=VP

c: \(VT=a\left(b-x\right)+x\left(a+b\right)\)

\(=ab-ax+ax+bx\)

\(=ab+bx=b\left(a+x\right)=VP\)

d: \(VT=a\left(b-c\right)-b\left(a+c\right)+c\left(a-b\right)\)

\(=ab-ac-ab-bc+ca-cb\)

\(=-2bc\)

=VP

3 Where was it made?

It was made in England

4 What was it made from?

It was made from wood and stone

6 Does your house have a moat?

Yes, it does