Find an equation of a hyperbola with vertices (-1, 3) and (-1, 7) and e = 4.
The eccentricity of a hyperbola is defined as e = c > a. For a hyperbola, c > a > 0, so e > 1 when e is close to 1, a hyperbola appears to be very narrow as the eccentricity increases, the hyperbola becomes "wider."