|x+1/1.2|+|x+1/2.3|+...+|x+1/99.100|=100x

2 câu trả lời

                  Bài giải :

|x+11×2|+|x+12×3|+...+|x+199×100|=100x.

Mà do vế trái luôn :x>0

x+11×2+x+23+x+34+.....+x+199×100=100x.

Vế trái có 99x

x=11×2+12×3+13×4+...+199×100.

x=1-12+12-13+13-14+...+199-1100.

x=1-1100.

x=99100.

|x+11.2|+|x+12.3|+...+|x+199.100|=100x(1)

Do {|x+11.2|0|x+12.3|0....|x+199.10|0(xR)

|x+11.2|+|x+12.3|+...+|x+199.100|0xR

Do đó : 100x0x0

Khi đó (1) có dạng :

x+11.2+x+12.3+...+x+199.100=100x(x+x+...+x)+(11.2+12.3+...+199.100)=100x99x+(112+1213+...+1991100)=100x99x+(11100)=100x99x+99100=100xx=99100x=99100(Tm)
Vậy x=99100