c d a c a c a c a d b a b d a

=x^4+1+2x^2+3x^3+3x+2x^2

=x^4+3x^3+4x^2+3x+2x^2

=x^3+x^3+2x^3+2x^2+2x^2+2x+x+1

=x^4+3x^3+4x^2+3x+1

Xét tứ giác ADHE có 

\(\widehat{ADH}=\widehat{AEH}=\widehat{EAD}=90^0\)

Do đó: ADHE là hình chữ nhật

Suy ra: Hai đường chéo AH và DE cắt nhau tại trung điểm của mỗi đường

=>IA=IH

hay I nằm trên đường trung trực của AH

2 bn

2

~ ckao cậu :)

Xét  \(\Delta HAB\) vuông tại H \(\left(AH\perp BC\right)\),ta có:

\(AB^2=AH^2+BH^2\left(ĐLPytago\right)\\ \Rightarrow BH^2=AB^2-AH^2\\ \Rightarrow BH=\sqrt{AB^2-AH^2}=\sqrt{7^2-2^2}=3\sqrt{5}\left(cm\right)\)

Xét  \(\Delta ABC\) vuông tại A và có AH là đường cao \(\left(AH\perp BC\right)\),ta có:

\(AH^2=BH.CH\left(HTL\right)\\ \Rightarrow CH=\dfrac{AH^2}{BH}=\dfrac{2^2}{3\sqrt{5}}=\dfrac{4\sqrt{5}}{15}\left(cm\right)\)

1.

⇒ He doesn't work as hard as me

⇒ He is lazier than me.

2. 

⇒ Your bedroom is more uncomforable than my bedroom.

⇒ Your bedroom is not as comfortable as my bedroom.

3. 

⇒ Mary speaks English better than John.

⇒ Mary doesn't speak English as worse as John.

4. No boy in my class are as intelligent as Jack.

5. They suggest that he should play football.

1. -> He doesn't work as hard as me.

    -> He works lazier than me.

2. -> Your bedroom isn't as comfortable as mine.

    -> Your bedroom is uncomfortable than mine.

3. -> Mary speaks English better than John.

   -> Mary doesn't speak English as bad as John.

4. -> No boy is as intelligent as Jack in my class.

5. -> They suggest playing football. 

a: k=70

b: y=70/x

a) Gọi a là hệ số tỉ lệ của x và y

Do x và y là hai đại lượng tỉ lệ nghịch nên xy = a

\(\Rightarrow a=7.10=70\)

b) Ta có:

xy = 70

\(\Rightarrow\) \(y=\dfrac{70}{x}\)

c) Khi x = 5 thì \(y=\dfrac{70}{5}=14\)

B2:

a) \(\dfrac{1}{x+2}+\dfrac{1}{\left(x+2\right)\left(4x+7\right)}\left(ĐK:x\ne-2;x\ne-\dfrac{7}{4}\right)\)

\(=\dfrac{4x+7}{\left(x+2\right)\left(4x+7\right)}+\dfrac{1}{\left(x+2\right)\left(4x+7\right)}\)

\(=\dfrac{4x+7+1}{\left(x+2\right)\left(4x+7\right)}\)

\(=\dfrac{4x+8}{\left(x+2\right)\left(4x+7\right)}\)

\(=\dfrac{4\left(x+2\right)}{\left(x+2\right)\left(4x+7\right)}\)

\(=\dfrac{4}{4x+7}\)

b) \(\dfrac{3x+5}{x^2-5x}-\dfrac{x-25}{25-5x}\left(ĐK:x\ne0;x\ne5\right)\)

\(=\dfrac{3x+5}{x\left(x-5\right)}+\dfrac{x-25}{5x-25}\)

\(=\dfrac{3x+5}{x\left(x-5\right)}+\dfrac{x-25}{5\left(x-5\right)}\)

\(=\dfrac{5\left(3x+5\right)}{5x\left(x-5\right)}+\dfrac{x\left(x-25\right)}{5x\left(x-5\right)}\)

\(=\dfrac{15x+25+x^2-25x}{5x\left(x-5\right)}\)

\(=\dfrac{x^2-10x+25}{5x\left(x-5\right)}\)

\(=\dfrac{x^2-2\cdot x\cdot5+5^2}{5x\left(x-5\right)}\)

\(=\dfrac{\left(x-5\right)^2}{5x\left(x-5\right)}\)

\(=\dfrac{x-5}{5x}\)

lỗi r bn

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