Thay \(x=-5\Rightarrow f\left(-5\right)=\frac{15}{-5}=-3\)

Thay \(x=-3\Rightarrow f\left(-3\right)=\frac{15}{-3}=-5\)

Thay \(x=-1\Rightarrow f\left(-1\right)=\frac{15}{-1}=-15\)

Thay \(x=1\Rightarrow f\left(1\right)=\frac{15}{1}=15\)

Thay \(x=3\Rightarrow f\left(3\right)=\frac{15}{3}=5\)

Thay \(x=5\Rightarrow f\left(5\right)=\frac{15}{5}=3\)

Thay \(x=15\Rightarrow f\left(15\right)=\frac{15}{15}=1\)

Vậy:

5.Mr.Brown speaks English . Mr.kent speaks English , too ( same language )

-> Mr.Brown speaks the same language as Mr Kent.

6. It is hot today . It was hot yesterday . ( like )

-> The weather today like the weather yesterday.

7.Mr.Phong teachers Math . Mr.Ha teachers History ( same subject )

-> Mr.Phong doesn't teach the same subject as Mr Ha.

8.The Royal Hotel is 400 meters high . The Qeen Hotel is 400 meters high , too ( Same height )

-> The Royal Hotel is the same height as the queen hotel.

9. I'm Vietnamese . She is Russian ( different )

-> My nationality is different from her nationality.

10. she sings more beautifully than her sister ( as...as)

-> Her sister doesn't sing as beautifully as her.

a) Xét \(\Delta AOH\left(\widehat{H}=90^o\right)\)và \(\Delta BOH\left(\widehat{H}=90^o\right)\) ta có:

\(OH\) là cạnh chung (gt)

\(\widehat{AOH}=\widehat{BOH}\) (gt)

\(\Rightarrow\Delta OAH=\Delta OBH\)

Vậy: \(OA=OB\) (2 cạnh tương ứng)

b) Xét \(\Delta OAH=\Delta OBH\)

\(\Rightarrow AH=BH\) (2 cạnh tương ứng) (1)

Xét \(\Delta CAH\) và \(\Delta CBH\)

CH là cạnh chung

\(\Rightarrow\Delta CHA=\Delta CHB\) (2 cạnh góc vuông)

=> CA = CB (2 cạnh tương ứng)

Ta có: \(\widehat{CAH}+\widehat{HAO}=\widehat{A}\)

Và \(\widehat{CBH}+\widehat{HBO}=\widehat{B}\)

Mà \(\widehat{CAH}=\widehat{CBH}\) (2 góc tương ứng)

Vì: \(\widehat{HAO}=\widehat{HBO}\) (2 góc tương ứng câu a)

Từ (1) (2) (3) suy ra \(\widehat{A}=\widehat{B}\)

chờ tí nhé!

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