Question

Write an equation of the cosine function with the given amplitude, period, phase shift, and vertical shift.

amplitude = 3, period = pi, phase shift = -3/4 pi, vertical shift = -3

Answer 1

y = + or - 3 cos (2 theta + 3/2 pi) - 3 is my answer

Answer 2

Looks good to me.
I'd go with the +3cos(2θ + 3π/2)-3
since the cosine function is what is being given, not a flipped or shifted cosine.