The slope-intercept form:
[tex]y=mx+b[/tex]
m - slope
b - y-intercept
The formula of a slope:
[tex]m=\dfrac{y_2-y_1}{x_2-x_1}[/tex]
We have the points (-1, 1) and (2, 13). Substitute:
[tex]m=\dfrac{13-1}{2-(-1)}=\dfrac{12}{3}=4[/tex]
Therefore the equation of a line is
[tex]y=4x+b[/tex]
Put the coordinates of the point (2, 13) to the equation of a line:
[tex]13=4(2)+b[/tex]
[tex]13=8+b[/tex] subtract 8 from both sides
[tex]5=b\to b=5[/tex]
