Answer:
a = 2
b = 4
Explanation:
4x² - y² = 16
General equation for a horizontal hyperbola:
(x-h)²/a² - (y-k)²/b² = 1
with center (h,k) & vertices (h±a,k)
Divide by the constant
4x²/16 - y²/16 = 1
x²/4 - y²/16 = 1
x²/2² - y²/4² = 1
center (h,k) = (0,0)
a = 2
b = 4