+212 The focus of a parabola is (3,−7) and the directrix is y=−4.
What is an equation of the parabola?
A. (x−3)2=−1.5(y+5.5)
B.(x−3)2=−12(y+10)
C.(x−3)2=−3(y+10)
D.(x−3)2=−6(y+5.5)
+128408 The focus is above the directrix....so this parabola turns downward
The vertex is given as ( 3, (-7 + -4) / 2 ) = (3, -5.5 )
And we have this equation
( x - h)^2 = 4p ( y - k) where the vertex is ( h, k) and p is the (negative) distance between the focus and the vertex and is given by:
p = ( -7 - - 5.5)
p = (-7 + 5.5)
p = -1.5
So...the equation is :
( x - 3)^2 = 4(-1.5) ( y + 5.5)
(x - 3)^2 = -6(y + 5.5) ⇒ Answer "D"
