Question

tìm x biết x là số tự nhiên (N)

 \(\frac{x}{12}\)=\(\frac{1}{x}\)x 3

Answer 1

\(\frac{x}{12}=\frac{3}{x}\Rightarrow12\cdot3=x^2\Rightarrow36=x^2\Rightarrow x=6\left(x\inℕ\right)\)

Answer 2

\(\frac{x}{12}=\frac{3}{x}\)

\(\frac{x}{12}.x=\frac{3}{x}.x\)

\(\frac{x^2}{12}=3\)

\(x^2=3.12=36\)

\(x=6\)

Answer 3

\(\frac{x}{12}=\frac{1}{x}.3\) 

\(x^2=12.3=36\) 

\(\Rightarrow x\in\left\{6;-6\right\}\) mà \(x\in N\) 

=> x=6

Vậy....