Answer:
 -2
Step-by-step explanation:
The range of the fizgig is -∞ to +∞. The range of the whatzit is -3 ≤ y < ∞. That is, both creatures pass through all y-values between -3 and +∞.
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Perhaps you want the y-coordinate of a point that both creatures pass through. The point of intersection is found where both equations are satisfied:
 2x -4 = y = x^2 -3
 x^2 -2x +1 = 0
 (x -1)^2 = 0
 x = 1
The value of y at that point is ...
 y = 2x -4 = 2(1) -4 = -2
The y-coordinate of the point both creatures pass through is -2.
