From the description you give, I assume you want to write an equation of the line with slope -5 and y-intercept (0,1). You can use the slope-intercept form for the equation of the line, which is
y =mx + b,
where m is the slope, and b is the y-coordinate of the y-intercept. In this example, m = -5 and b = 1. Therefore, the equation of the line is
y = -5x + 1
Hope that helps!