To derive the equation of the line in the form \( y = mx \) that goes through the origin, we first need to determine the slope \( m \) of the line given the two points: \( (1, 5) \) and \( (2, 10) \).
The formula for the slope \( m \) is:
\[ m = \frac{y_2 - y_1}{x_2 - x_1} \]
Substituting the coordinates of the points:
\[ m = \frac{10 - 5}{2 - 1} = \frac{5}{1} = 5 \]
Now that we have the slope, we can write the equation of the line through the origin in the form:
\[ y = mx \]
Substituting \( m \):
\[ y = 5x \]
Therefore, the equation of the line is:
\[ \boxed{y = 5x} \]