What's the equation of the parabola that has its vertex at (5,–1) and a y-intercept at (0,–27⁄2)? a. y = –1⁄2(x + 5)2 – 1 b. y = 1⁄2(x – 5)2 + 1 c. y = 1⁄2(x – 5)2 – 1 d. y = –1⁄2(x – 5)2 – 1