SOLUTION: Consider the parabola y=x^2 +4x-3. Find the equation of the directrix.
One of the following is correct. Which one is correct?
A) y=-7
B) y=-7.25
C) y=-8
D) y=-7.75
Algebra.Com
Question 1199102: Consider the parabola y=x^2 +4x-3. Find the equation of the directrix.
One of the following is correct. Which one is correct?
A) y=-7
B) y=-7.25
C) y=-8
D) y=-7.75
Answer by greenestamps(13200) (Show Source): You can put this solution on YOUR website!
Complete the square to put the equation in vertex form. Vertex form is
The vertex is (h,k); p is the directed distance from the directrix to the vertex and from the vertex to the focus.
The vertex is (-2,-7); 1/(4p) = 1, so p = 1/4.
The parabola opens upward, so the directrix is p units below the vertex: -7 - 1/4 = -7.25.
ANSWER B) y=-7.25
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