in the equation y = 2x + 4, you know that the gradient is 2 (the number before x).
for a perpendicular line you need the negative reciprocal of 2, which is -

.
you then need to use the equation
y -

= m(x -

)
substitute in your coordinates:
y - -2 = -

(x - 3)
simplify:
y + 2 = -0.5x + 1.5
rearrange:
y = -

-
