\(331=\left(x+140\right).\frac{1}{x}+260\)
\(\left(x+140\right).\frac{1}{x}+260-331=0\)
\(\left(x+140\right).\frac{1}{x}-71=0\)
\(\frac{1}{x}.x+\frac{1}{x}.140-71=0\)
\(1+\frac{1}{x}.140=0\)
\(\frac{1}{x}.140=0-1=-1\)
\(\frac{1}{x}=-\frac{1}{140}\Rightarrow x=1:-\frac{1}{140}=-140\)
\(71+260=\frac{x+140+260x}{x
}\)
\(331=\frac{261x+140}{x}\)
\(331x=261x+140\)
\(70x=140\)
\(x=2\)
Nhớ thêm dấu khi và chỉ khi <=> trước mỗi phép kia nhé, mình lười quá không ghi
331= [x+140]:x+260 hay [x+140]:x+260=331
x/x + 140/x + 260 = 331
1 + 140/x + 260 = 331
1 + 140/x = 331 - 260
1 + 140/x = 71
140/x = 71 - 1
140/x = 70
=> x = 140 : 70 = 2
