?????? cái này cx phải hỏi ư?

(x+1)+(x+2)+(x+3)+...+(x+100)=205550

x+1+x+2+x+3+...+x+100=205550

 100x+(100+1).100:2=205550

100x+5050=205550

100x=200500

x=2005

a)     (x+1)+(x+2)+(x+3)+.....+(x+100)=205550

       \(\left(\frac{100-1}{1}\right)+1\)=100(ngoặc)

        100X+(1+2+3+.....+100)=205550

        100X+5050=205550

        100X=205550-5050

         100X=200500

        X=2005

còn lại tự làm và thêm văn võ chut ít vào đó nhé!      

75:(x-8)=5

x-8       = 75:5

x-8       =15

x           = 15+8

x           =23

75/(x-8)=5

=> x-8=75:5

=> x-8=15

=> x=15+8

=> x=23

nhanh lên

    Mình thích môn Thể Dục cơ =)) Nhưng cứ viết cho bạn về môn Tiếng Anh 

 My favorite subject is English. The first reason I like this subject is that itis a core subject which is vital and essential in my career path. I try to learn thisinternational language well so that I can communicate with foreigners and find agood job in the future. Furthermore, learning English well can help me readbooks or magazines in English. Through reading things in English, I can beexposed to various cultures and customs. Besides, my English teacher is adedicated person who can engage me in her lessons and bring the passion for me.I found her lessons interesting because she delivered them in a way that I reallyliked. In short, English is an important subject which I am really keen on.

4 điều nên viết:
1. What subject
2. What it deals with
3. Why I like it
4. The end

I learn many subjects in school. But the one I enjoy learning is History.

History helps us know what people did and how they lived ages ago. It also tells us how men had to manage to make their lives better and better.

Many learners, however, do not like to read History. They say that there are too many names and dates to remember. But they do not understand that if we know nothing about the past, we cannot have a good knowledge of the present. For example, if we wish to know how men learnt to use fire or clothes, we have to know what men did in the past to travel at night or to keep themselves warm. In fact, only a study of History will make us realize that what we do today is the result of what our ancestors did in the past. History therefore is a long story of man’s struggle through the ages. As we read the story, we are learning many interesting things.

I enjoy learning history. I have a large number of history books in my house. Some day, I might even write a history book myself.

Thanks 

Gọi số đó là a

0,25 = \(\frac{1}{4}\)

a : \(\frac{1}{4}\)- 1,5 = a x \(\frac{1}{4}\)+ 1,5

a x 4 - 1,5 = a x \(\frac{1}{4}\)+1,5

a x 4 - a x \(\frac{1}{4}\)= 1,5 + 1,5

a x \(\left(4-\frac{1}{4}\right)\)= 3

a x \(\frac{15}{4}\)= 3

\(a=3\div\frac{15}{4}\)

\(a=\frac{4}{5}=0,8\)

Đáp số : 0,8

Gọi số đó là a
ta có: a/0,25-1,5=a*0,25+1,5
         4a-0,25a=3
         3,75a=3
               a=0,8

đặt tên biểu thức là S . Ta có :

S = 3x4 + 4x5 + 5x6 + ... + 99x100

3S = 3x4x3 + 4x5x3 + 5x6x3 + ... + 99x100x3

3S = 3x4x(5-2 ) + 4x5x(6-3) + 5x6x(7-4) + ... + 99x100x(101-98)

3S = 3x4x5-2x3x4 +  4x5x6-3x4x5 + 5x6x7 - 4x5x6 + ... + 99x100x101 - 98x99x100

3S = 99x100x101 - 2x3x4

3S = 3 x ( 33x100x101-2x4 )

S = 33x100x101-2x4

S = 333300 - 8

S = 333292

Đặt A = 3.4 + 4.5 + 5.6 + ... + 99.100

3A = 3.4.(5-2) + 4.5.(6-3) + 5.6.(7-4) + ... + 99.100.(101-98)

3A = 3.4.5 - 2.3.4 + 4.5.6 - 3.4.5 + 5.6.7 - 4.5.6 + ... + 99.100.101 - 98.99.100

3A = 99.100.101 - 2.3.4

3A = 3.(33.100.101 - 2.4)

A = 33.100.101 - 2.4

A = 333300 - 8

A = 333292

Đặt S = 3.4 + 4.5 + 5.6 + ..... + 99.100

=> 3S = 3.4.(5 - 2) + 4.5.(6 - 3) + .... + 99.100.(101 - 98)

=> 3S = 3.4.5 - 3.4.5 + 4.5.6 - 4.5.6 + ..... + 99.100.101 - 2.3.4

=> 3S = 99.100.101 - 2.3.4

=> 3S = 999900 - 24

=> 3S =  999876

=> S = 999876 : 3

=> S = 333292