First, we need to find the slope of line a, using the next formula
[tex]m=\frac{y_2-y_1}{x_2-x_1}[/tex]where
(1,-4)=(x1,y1)
(9,-6)=(x2,y2)
we substitute the values
[tex]m=\frac{-6+4}{9-1}=\frac{-2}{8}=-\frac{1}{4}[/tex]The slope of a perpendicular line to line a is the inverse of the slope we found therefore the slope of line b will be
[tex]m_b=4[/tex]then we will use the slope-point form to find the equation of line b
[tex]y-y_1=m(x-x_1)[/tex]where
(-6,-24)=(x1,y1)
[tex]y+24=4(x+6)[/tex]then in order to find the equation in the slope-intercept form, we need to isolate the y
[tex]\begin{gathered} y+24=4x+24 \\ \end{gathered}[/tex][tex]y=4x+24-24[/tex][tex]y=4x[/tex]The equation of line b is y=4x