Equation of a line in slope-intercept form is



where m is the slope and c is the intercept of the line on y-axis

Also, the equation of a line in point-slope form is



Where is the point and m is the slope.

Since the slope of a line passing through two points can be found out using



Therefore, we can find out the equation of the line using point-slope form.

Therefore, Helena is correct since we cannot find out the intercept c and hence Samuel's method is incorrect,