Ta có :
\(\frac{6\frac{1}{4}}{x}=\frac{x}{1,96}\)
\(\Leftrightarrow\frac{\frac{25}{4}}{x}=\frac{x}{1,96}\)
\(\Rightarrow x^2=\frac{25}{4}.1,96\)
\(\Leftrightarrow x^2=\frac{49}{4}\)
\(\Leftrightarrow x=\sqrt{\frac{49}{4}}\)
\(\Rightarrow x=\frac{7}{2}\)
P/s tham khảo nha