1 I'm not really interested in robotics.

2 We might go to the moon for our summer holiday in 2050.

3 I couldn't email you last night because my computer didn't work.

4 I didn't need to finish my homework yesterday.

5 She has worked at the school canteen for two months.

6 If you don't study hard, you won't pass the exam.

\(\left(x^2-1\right)'=2x;\left[\left(x-2\right)^4\right]'=4\cdot\left(x-2\right)^3\cdot\left(x-2\right)'=4\left(x-2\right)^3\)

\(f''\left(x\right)=\left(x^2-1\right)'\left(x-2\right)^4+\left(x^2-1\right)\left[\left(x-2\right)^4\right]'\)

\(=2x\left(x-2\right)^4+\left(x^2-1\right)\cdot4\left(x-2\right)^3\)

\(=2\left(x-2\right)^3\left[x\left(x-2\right)+2x^2-2\right]\)

\(=2\left(x-2\right)^3\left(3x^2-2x-2\right)\)

Đặt \(f'\left(x\right)=0\)

=>\(\left[{}\begin{matrix}x=1\\x=-1\\x=2\end{matrix}\right.\)

\(f''\left(2\right)=0;f''\left(1\right)=2>0;f''\left(-1\right)=-162< 0\)

=>Chọn B 

câu 1:Hai nhân vật trên vi phạm phương châm về chất.Đặc điểm nhận biết đó chính là qua lời nói của hai người,nói không đúng sự thật,không có chứng cứ xác thực

câu 2:a) Câu ấy vi phạm phương châm về lượng vì bồ câu thì đương nhiên là loài chim có hai cánh nên không cần nói có hai cánh người đọc cũng tự hiểu được

b) Phương châm lịch sự (mk ko chắc nữa)

câu 12 :A

câu 13 :B

câu 14 :D

câu 15 :A

câu 16 :D

câu 17 :A

câu 18 :C

câu cuối mik chx chắc lắm 

a: Xét ΔAFD vuông tại F và ΔCEB vuông tại E có

AD=CB

góc FAD=góc ECB

=>ΔAFD=ΔCEB

=>DF=EB

Xét tứ giác DFBE có

DF//BE

DF=BE

=>DFBE là hình bình hành

b: S CAB=S CAD

=>CH*AB=CK*AD

=>CH*AB=CK*BC

=>CH/BC=CK/AB

Xét ΔCHK và ΔBCA có

CH/BC=CK/BA

góc HCK=góc CBA

Do đó: ΔCHK đồng dạng với ΔBCA

refer

1 . Electricity will be brought to remote areas by the government next year

2 . The problem of energy shortage will be solved by using solar energy

3 . A new hydropower plant will be built to meet the increasing demand by the government

4 . In the coming decades , renewable energy will be used everyday /

5 . Will all the world's oil be used up in the next 100 years ?

6 . Solar panels will be placed on the roofs of houses to produce hot water and electricity

7 . Cold , oil , and gas won't be replaced by alternative energy sources anytime soon

8 . Will fossil fuels be completely replaced by renewable energy in the future ?

1 . Electricity will be brought to remote areas by the government next year

2 . The problem of energy shortage will be solved by using solar energy

3 . A new hydropower plant will be built to meet the increasing demand by the government

4 . In the coming decades , renewable energy will be used everyday /

5 . Will all the world's oil be used up in the next 100 years ?

6 . Solar panels will be placed on the roofs of houses to produce hot water and electricity

7 . Cold , oil , and gas won't be replaced by alternative energy sources anytime soon

8 . Will fossil fuels be completely replaced by renewable energy in the future ?