y TLT với x suy ra: y=kx
\(\Rightarrow k=\frac{y}{x}\)
\(\Rightarrow k=\frac{y_1}{x_1}=\frac{y_2}{x_2}\Rightarrow\left(\frac{y_1}{x_1}\right)^2=\left(\frac{y_2}{x_2}\right)^2\Rightarrow\frac{\left(y_1\right)^2}{\left(x_1\right)^2}=\frac{\left(y_2\right)^2}{\left(x_2\right)^2}\)
\(\Rightarrow k=\frac{\left(y_1\right)^2-\left(y_2\right)^2}{\left(x_1\right)^2-\left(x_2\right)^2}=\frac{400}{25}=16\)
Vậy hệ số tỉ lệ là 6