You're the best

Lan is my best friend

cứ làm đi 3 con tích sẽ về ngay tay bn

Bài 1:

G/s ngược lại: \(ad=bc\) , ta cần CM giả thiết.

Ta có: \(ad=bc\) => \(\frac{a}{b}=\frac{c}{d}=k\Rightarrow\hept{\begin{cases}a=bk\\c=dk\end{cases}}\) \(\left(k\inℤ\right)\)

Thay vào:

\(\left(a+b+c+d\right)\left(a-b-c+d\right)\)

\(=\left(bk+b+dk+d\right)\left(bk-b-dk+d\right)\)

\(=\left(k+1\right)\left(b+d\right)\left(k-1\right)\left(b-d\right)\) (1)

\(\left(a-b+c-d\right)\left(a+b-c-d\right)\)

\(=\left(bk-b+dk-d\right)\left(bk+b-dk-d\right)\)

\(=\left(k-1\right)\left(b+d\right)\left(k+1\right)\left(b-d\right)\) (2)

Từ (1) và (2) => GT được CM => đpcm

H M B A C D E I

It's coffin.

reasonable

c, ta có: \(2^{4n+2}\)+1\(⋮\)5

=> (...6).(\(2^2\))+1\(⋮\)5 

=>(...6).4+1\(⋮\)5

=>(...24)+1\(⋮\)5

=>(...25)\(⋮\)5 =>(đpcm)

XV. Reorder the words to make meaningful sentences
. 1. V cheat/ never/ will/ the/ promisel exam/ that1/ in anymore.=>V  promise that will never cheat the exam anymore (câu này bạn chép vào hình như không đủ câu hoặc thiếu chéo)
2. swim/ she/ after/ able/ will/ be/ to/ praces/ hard two/ i0 shel weeks.=> She will be able to praces swim hard in two week  

3. we/ if our/ planta environment/ bel greener/ more/ trees will=>If we plant more trees,our environment will be more greener

. 4. fly/ I/ my/ buy/ a ket/ to / could/ to New York/ holiday for.=> I could buy a ket fly to New York for my holiday

5. take/ this/ probably/ he/ environment/ will part/ in/ campaign.=> He probaly will take part in this environment campaign

. XVI. Rewrite the sentences based on the given words helow

. 1.1 was able to ride a bicycle when I was 7 years old(Câu này không có từ cho ?)

.I I couldn't visit Glasgow because I didn't have enough time.I.. (able) => I can't be able visited  Glasgow because have enough time

3. I want to have a private tutor. I will learn better. IfI have =>If I have a private tutor,I will learn better

4. Some robots in the future will have the ability to do all the housework. Some robots . (able) => Some robots will be able have the ability to do all the house work

5. Maybe he will paripate in this recycling campaign. -> He will... (probably

What would she ?

She'd some water

<=> What some she did ?

D(-2,5;2,5) chứ

Haiz, đề đúng mà.