\(A1+2=A2\)

   \(\overline{A}\) =\(\dfrac{A1\cdot54+\cdot\left(A1+2\right)\cdot46}{100}\)=79.92

\(\Leftrightarrow\)A1=79\(\Rightarrow\)A2=81  

Thanksss bann nhiều lắm nhoa

1 When do they do their homework?

2 Who came to the party aloe

3 Which blouse do you like

4 How did she feel after she took a nap

5 How long did she talk to him

6 How many cars do your parents have

7 When are they coming to visit you?

8 Who is your brother

9 Why don't you get up early?

10 How often do you have an English class

Gọi tâm của (C) là I(x;y)

(C) tiếp xúc với (Δ) tại A(1;-1)

=>IA⊥(Δ)

=>IA: x+2y+c=0

Thay x=1 và y=-1 vào IA, ta được:

1+2*(-1)+c=0

=>1-2+c=0

=>c-1=0

=>c=1

=>IA: x+2y+1=0

=>x=-2y-1

=>I(-2y-1;y)

I(-2y-1;y); A(1;-1); B(4;0)

\(IA=IB\)

=>\(IA^2=IB^2\)

=>\(\left(-2y-1-1\right)^2+\left(y+1\right)^2=\left(-2y-1-4\right)^2+\left(y-0\right)^2\)

=>\(\left(-2y-2\right)^2+\left(y+1\right)^2=\left(-2y-5\right)^2+y^2\)

=>\(4y^2+8y+4+y^2+2y+1=4y^2+20y+25+y^2\)

=>10y+5=20y+25

=>-10y=20

=>y=-2

=>x=-2y-1=-2*(-2)-1=4-1=3

=>I(3;-2)

I(3;-2); B(4;0)

\(IB^2=\left(4-3\right)^2+\left(0+2\right)^2=1^2+2^2=5\)

Phương trình(C) là:

\(\left(x-3\right)^2+\left(y+2\right)^2=IB^2=5\)

a)Hóa trị 4

b)Ba hóa trị 2

a) Mn hóa trị IV

b) Ba hóa trị II

1 had gone to bed, we watched television

2 had a swim for 5 days

3 met him for 5 months

4 gone to this club since 1999

5 come to this city since July

6 learned French since 2001

7 played chess for 3 years

8 smoked for 5 years

9 there, Jack had left the office

10 I have visited England

11 the first time I have met this lady

12 I was having dinner, the phone rang

13 we arrived there, David had left the party

14 used to wear glasses before

15 ages since we last went to a concert

16 saw her friends when she left for the United states

17 the first time I have stayed in such an expensive hotel

1 After the children had gone to bed, we watched television

2 She hasn't had a swim for 5 years

3 I haven't met him for 5 months

4 Tom hasn't gone to this club since 1999

5 They haven't come to this city since July 

6 Tom has learned French since 2001

7 She has played chess for 3 years

8 He hasn't smoked for 5 years

9 When I arrived at the office, Jack had left there

10 This is the first time I have visited England

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