The slope-intercept form:
[tex]y=mx+b[/tex]
m - slope
b - y-intercept
We have the slope [tex]m=3\to y=3x+b[/tex]
and point (1, -1). Substitute:
[tex]-1=3(1)+b[/tex]
[tex]-1=3+b[/tex] subtract 3 from both sides
[tex]-4=b\to b=-4[/tex]
Answer: [tex]y=3x-4[/tex]