The slope-intercept form:
[tex]y=mx+b[/tex]
m - slope
b - y-intercept → (0, b)
We have the point (0, 5). Therefore b = 5.
We have: y = mx + 5
Other point (3, 2). Substitute the coordinates of the point to the equation of the line:
[tex]2=3m+5[/tex] subtract 5 from both sides
[tex]-3=3m[/tex] divide both sides by 3
[tex]-1=m\to m=-1[/tex]
Answer: f(x) = -1x + 5 = -x + 5
