51x - ( 1+2+3+4+....+50) = 255

51x - 1275 = 255

51x = 255 + 1275

51x = 1530

x= 1530 : 51 

x =30

x+x-1+x-2+x-3+x-4+...+x-50 = 255

c) x+x-1+x-2+x-3+...+x-50=255

51x-(50+49+48+...+1)=255

51x-1275=255

51x=255+1275

51x=1530

x=1530:51

x=30

x=30,52

*^*(&()*)(^*&%&^%*(

x+(x-1)+(x-2)+....+(x-50)=225

<=>x+x-1+x-2+...+x-50=225

<=>51x-1275=225

<=>51x=-1050

bạn nè, câu trả lời của Nguyễn Quốc Khánh là sai đó

x+(x-1)+(x-2)+...+(x-50)=255

x+(x+x+x+.....+x)-(1+2+3+...+50)=255

x+50x-1275=255

51x-1275

51x=1275+255

51x=1530

x=1530/51

x=30

trong phep chia cho 3 4 5 so du co the la bao nhieu

x + ( x - 1 ) + ( x - 2 ) + ... + ( x - 50 )

<=> x + x - 1 + x - 2 + ..... + x - 50 = 255

<=> 51x - 1275 = 255

<=> 51x = -1050

P/s: Sai thì bn sửa lại nha

51x - [1+2+3+...+50] =255

=> 51x - 50 x 51 : 2 = 255

=> 51x - 1275 =255

=> 51x = 1530 

=> x = 30

\(51x-\left(1+2+3+..+50\right)=255\)

\(51x-\frac{51.50}{2}=255\)

\(51x-1275=255\)

\(\Rightarrow51x=255+1275\)

\(\Rightarrow51x=1530\)

\(\Rightarrow x=30\)

\(51x-\left(1+2+3+...+50\right)=255\)

\(51x-\frac{50.51}{2}=255\)

\(51x-1275=255\)

\(\Rightarrow51x=255+1275\)

\(\Rightarrow51x=1530\)

\(\Rightarrow x=30\)

x+x-1+x-2+x-3+....+x-50 = 255

x+x+x+...+x - (1+2+3+...+50) = 255

51x - 1275 = 255

=> 51x = 1530

=> x = 30

x + (x - 1) + (x - 2) + ... + (x - 50) = 255

=> (x + x + x + ... + x) - (0 + 1 + 2 + ... + 50) = 255

            51 số x                    51 số hạng

=> 51x - (0 + 50).51:2 = 255

=> 51x - 50.51:2 = 255

=> 51x - 25.51 = 255

=> 51.(x - 25) = 255

=> x - 25 = 255 : 51

=> x - 25 = 5

=> x = 5 + 25 

=> x = 30

Vậy x = 30