find the equation of the line (3, -5) and (-1,2)

i did it and got an equation y = -7/4x + 1/4

how its asking to find the equation of the normal of this line at point (3, -5)

how do i get that?

i know u use m1 and m2, u have y = m2x + b.. how do u work out b?

m2 = 4/7 and x = 3 but b ?

thank u!!