The slope-intercept form:
[tex]y=mx+b\\\\m=\dfrac{y_2-y_1}{x_2-x_1}[/tex]
We have (1, -7) and (-1, 1).
Substitute:
[tex]m=\dfrac{1-(-7)}{-1-1}=\dfrac{8}{2}=4[/tex]
Therefore we have
[tex]y=4x+b[/tex]
Substitute the coordinates of the first point to the equation of line:
[tex]-7=-4(1)+b[/tex]
Answer:
[tex]\dfrac{1+7}{-1-1}=-4;\ -7=-4(1)+b[/tex]
