Vth = 0  # (4vx = 20*(-vx/5))
# set vab = vo, solve io
# let mesh current equals i
# i*15 + 4*(-i*5) + (i + io)*15 = 0
# 15*(-io - i) + vo = 0
Rth = -7.5

print(f"Vth and Rth is {Vth} V and {Rth} ohm, respectively.")

