The slope-intercept form:
[tex]y=mx+b[/tex]
m - slope
b - y-intercept
We have the slope [tex]m=\dfrac{1}{2}\to y=\dfrac{1}{2}x+b[/tex]
and point (4, 0). Substitute:
[tex]0=\dfrac{1}{2}(4)+b[/tex]
[tex]0=2+b[/tex] subtract 2 from both sides
[tex]-2=b\to b=-2[/tex]
Answer: [tex]y=\dfrac{1}{2}x-2[/tex]