Unit 3 : At home

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a) Do `{(AM ⊥z),(KC ⊥z):}`

`=> AM` // `KC  `

b) Do `AM` // `KC `

`=> hat{AMK} = hat{MKC}` (2 góc so le trong)

Mà `hat{AMK} = 30^o`

`=> hat{MKC} =  30^o`

c) Kẻ `Bt ` // `MA ` (`Bt` hướng về bên trái)

Do `Bt` // `MA`

`=> hat{AMB} + hat{MBt} = 180^o` (2 góc trong cùng phía) 

`=> 30^o + 80^o +  hat{MBt} = 180^o`

`=>  hat{MBt} = 70^o`

Do `MA` // `KC => Bt` // `KC `

`hat{CBt} + hat{BCK} = 180^o` (2 góc trong cùng phía) 

`=> hat{CBt} + 160^o = 180^o`

`=> hat{CBt} = 20^o`

Khi đó: `hat{MBC} = hat{MBt} +  hat{CBt} = 70^o + 20^o = 90^o`

`=> BC ⊥ MB (đpcm)`

\(\left(\dfrac{1}{125}-x^3\right)\left(x^2+2^2\cdot2^6\right)=0\)

mà \(x^2+2^2\cdot2^6>0\forall x\)

nên \(\dfrac{1}{125}-x^3=0\)

=>\(x^3=\dfrac{1}{125}\)

=>\(x=\sqrt[3]{\dfrac{1}{125}}=\dfrac{1}{5}\)

\(\left(\dfrac{1}{125}-x^3\right)\left(x^2+2^2.2^6\right)=0\)

\(\Rightarrow\left(\dfrac{1}{125}-x^3\right)\left(x^2+2^8\right)=0\)

Vì \(x^2+2^8>0\forall x\)

\(\Rightarrow\dfrac{1}{125}-x^3=0\)

\(\Rightarrow x^3=\dfrac{1}{125}\)

\(\Rightarrow x=\dfrac{1}{5}\)

a: ta có: \(\widehat{xCD}=\widehat{mCA}\)(hai góc đối đỉnh)

mà \(\widehat{mCA}=60^0\)

nên \(\widehat{xCD}=60^0\)

b: Ta có: \(\widehat{BDC}+\widehat{yDC}=180^0\)(hai góc kề bù)

=>\(\widehat{BDC}=180^0-120^0=60^0\)

Ta có: \(\widehat{xCD}=\widehat{CDB}\left(=60^0\right)\)

mà hai góc này là hai góc ở vị trí so le trong

nên Ax//Dy

=>Ax//By

c: ta có: Ax//By

Ax\(\perp\)AB

Do đó: By\(\perp\)AB

9)\(\left|\dfrac{3}{4}x-\dfrac{3}{4}\right|\)=\(\left|\dfrac{-3}{4}\right|\)

⇒\(\left|\dfrac{3}{4}x-\dfrac{3}{4}\right|\)=\(\dfrac{3}{4}\)

TH1: \(\dfrac{3}{4}x-\dfrac{3}{4}\)=\(\dfrac{-3}{4}\)⇒\(\dfrac{3}{4}\)x=\(\dfrac{3}{4}\)+\(\dfrac{-3}{4}\)=0

                              ⇒x=0

TH2:\(\dfrac{3}{4}\)x-\(\dfrac{3}{4}\)=\(\dfrac{3}{4}\)⇒\(\dfrac{3}{4}\)x=\(\dfrac{3}{4}\)+\(\dfrac{3}{4}\)=\(\dfrac{3}{2}\)⇒x=\(\dfrac{3}{2}\):\(\dfrac{3}{4}\)=2

`|3/4 x - 3/4| = |(-3)/4|`

`<=> 3/4 . |x - 1| = 3/4 . |-1| `

`<=> |x - 1| = |-1| `

`<=> |x - 1| = 1`

`<=> x - 1 = 1` hoặc `x - 1 = -1`

`<=> x = 2` hoặc `x = 0`

Vậy....

PN/NV là cái gì c?

1.Fruit and vegetables have a lot of vitamins.

2.He has bread and egg for breakfast.

3.Playing video games isn't as good as exercising.

4.He is more intelligent than his friend

Volunteer work can bring us a lot of benefits

He taught English to a group of street children last summer

They often clean up the dirty river to protect the environment

We are collecting books and clothes for the poor children

Volunteers deliver meals every Sunday morning to the elderly and sick people 

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