1.Tìm x

a)\(x^2+9y^2-4x+6y+5=0\)

b)\(2x^2+2xy+y^2-6x-4y+5=0\)

2.Cho A = \(a^4+b^4+c^4-2a^2b^2-2b^2c^2-2a^2c^2\)

Chứng minh

a) Nếu a,b,c là độ dài 3 cạnh tam giác thì A < 0

b) Nếu A<0 và a,b,c là các số dươn thì a,b,c là độ dài 3 cạnh 1 tam giác

I.Tính

B=2021-\(\dfrac{5}{3}-\dfrac{5}{6}-\dfrac{5}{10}-\dfrac{5}{15}-\dfrac{5}{21}-\dfrac{5}{28}-\dfrac{5}{36}-\dfrac{5}{45}\)

II.Tìm 3 số a,b,c biết \(\dfrac{3a-2b}{5}=\dfrac{2c-5a}{3}=\dfrac{5b-3c}{2}\) và a+b+c=-50

III.Cho M=\(\dfrac{a}{a+b}+\dfrac{b}{b+c}=\dfrac{c}{c+a}\) với a,b,c là các số dương.Chứng minh M không phải là số nguyên

Tìm GTNN

A=\(|x+5|+2-x\)

B=\(|2x-1|+2x+6\)

C=\(|x-2|+|x-6|+5\)

D=\(|x+3|+|2x-5|+|x-7|\)

Mình đag cần gấp,mong các bạn giúp

I.Read the passage and answer the questions with the given words and answer them

Many people who work in London prefer to live outside it, and to go to their offices, factories or schools every day by train, car or bus, even though this means they have to get up earlier in the morning and come home later in the evening.
One advantage of living outside London is that houses are cheaper. Even a small flat in London without a garden costs quiet a lot to rent. With the same money, one can get a little house in the country with a garden of one's own.
Then, in the country one can rest from the noise and hurry of the town. Although one has to get up earlier and spend more time in trains or buses, one can sleep better at night, and during weekends. In summer evenings one can enjoy the fresh, clean air of the country. If one likes gardens, one can spendone's free time digging, planting, watering and doing the hundred and one other jobs which are needed in a garden.Then,when the flowers and the vegetables come up,one has the reward of want who shared the secrets of Nature.

1.Where/most people/work/London/prefer/live?

_______________________________________________________

_______________________________________________________

2.How/they/get/offices/factories/school/every day?

_______________________________________________________

_______________________________________________________

3.What/advantages/live/country?

_______________________________________________________

_______________________________________________________

4.Why/country air/good/health?

_______________________________________________________

_______________________________________________________

Cho \(\dfrac{a}{b}=\dfrac{c}{d}\)

Chứng minh \(\dfrac{a^2}{b^2}=\dfrac{2c^2-ac}{2d^2-bd}\)

I.Điền dạng đúng

1.Y and Y members also help the __________(old) and street children.

2.By recycling we can save ___________(nature) resouces.

3.There wasn't any ____________(electric) in our village many years ago.

4.He was _________(fool) to say that.

5.All the dancers wore _____________(tradition) costumes.

6.The World Health ___________(organize) is an international one.

II.Viết lại theo chỉ dẫn.

1."Read the instructions before yoou switch on the machine." He said to me.

He told _____________________________________________________.

2.The student asked many questions.He wantedto understand the lesson.

___________________________________________________________.(in order)

3.That old man usually darank lots of wine.

_______________________________________.(used to)

III.Điền từ thích hợp vào chỗ trống.

themselves,althought,handocapped,encourage,along,neither

1._________each nation's scouting program differs slightly.

2.Don't _________ bad habbits in a child.

3.Peter and Susan can __________speak not hear.They are ___________ children.

Tính

A=\(\dfrac{4^5x9^4-2x6^9}{2^{10}x3^8+6^8x20}\)

\(\dfrac{1}{1x2x3}+\dfrac{1}{2x3x4}+...+\dfrac{1}{2015x1016x1017}\)

CHÚ Ý: \(x\) là dấu nhân nhé.Sáng mai mk phải nộp rồi.Mong các bạn giúp mk nha!Mơn nhiều

I.Tính giá trị

C=\(1^2+3^2+...+99^2\)

D=\(2^2+4^2+...+100^2\)

E=\(1^2+2^2+3^2+....+99^2+100^2\)

II.Tính

\(\dfrac{3}{\left(1x2\right)^2}+\dfrac{5}{\left(2x3\right)^2}+...+\dfrac{19}{\left(9x10\right)^2}\)

CHÚ Ý:x là dấu nhân nhá.Mk đag cần gấp lắm.Các bạn giúp mk nhé!

Sắp xếp lại câu.

1.warm/go/the children/not/swimming/the weather/to/was/for/enough.

________________________________________________________________.

2.collectors'/morning/brother/attend/meeting/going/tomorrow/my/a/to/is/stamp.

________________________________________________________________.

3.ought/on/the room/put/side/we/right/of/the closet/put/to.

_________________________________________________________________.

4.the meals/her/Hoa/when/coudin/cook/with/used/lived/to/she.

_________________________________________________________________.

5.because/difficult/answer/them/the questions/too/I/all/were/could't/of/some.

_________________________________________________________________.