Question

tìm x

a)  1+ 2 + 3 + 4 + ...........  + X = 55

b) 1* x + 2 * x + 3 * x + 4 * x ........... + 100 * x = 505000

              giải chi tiết lun nha mấy bạn thank you

 

Answer 1

a, 1 + 2 + 3 + 4 + .... + x = 55 

\(\Rightarrow\frac{\left(x+1\right)\left[\left(x-1\right)+1\right]\text{ }}{2}=55\)

\(\Rightarrow\left(x+1\right)\left[\left(x-1\right)+1\right]=110\)

\(\Rightarrow\left(x+1\right)\left(x-1\right)=110\)

Đề sai :))) 

Answer 2

b) \(1.x+2.x+3.x+4.x+...+100.x=505000\)

\(x.\left(1+2+3+4+...+100\right)=505000\)

\(x.\frac{\left(100+1\right).\left[\left(100-1\right)+1\right]}{2}=505000\)

\(x.5050=505000\)

\(x=100\)

Vậy \(x=100\)

Answer 3

cảm ơn các bạn nhiều lắm