Answer
You want to find the equation for a line that has a slope of 4 and a y-intercept of -1.
First of all, remember what the equation of a line is:
y = mx+b
Where:
m is the slope, and
b is the y-intercept
All you really have to do here is
replace m with 4, which is the slope you gave, and
replace b with -1, the y-intercept you gave,
in the equation y=mx+b.
The equation of the line that has a slope of 4 and a y-intercept of -1 is:
y=4x-1.