Question

Identify the vertex and directrix of each. y = x2 + 2x - 4

Answer 1

Answer:

See below

Step-by-step explanation:

Convert equation to vertex form $y=(x-h)^2+k$ by completing the square:

$y=x^2+2x-4$

$y+5=x^2+2x-4+5$

$y+5=x^2+2x+1$

$y+5=(x+1)^2$

$y=(x+1)^2-5$

Vertex:

$(h,k)\rightarrow(-1,-5)$

Directrix:

$y=k-\frac{1}{4a}\rightarrow y=-5-\frac{1}{4(1)}\rightarrow y=-\frac{21}{4}$