Page 9 - Jose Garcia_2013150017_grade12 ebook

2
 ( − 4) = 12 ( – 2)
2
 – 8 + 16 = 12 – 24

2
 y – 8 – 12 + 40 = 0

The directrix equation is = –

 x = 2 – 3

 = − 1

 + 1 = 0

The graphic sketch is …….

2. Find the equation of a parabola with the vertex (1, -3) and the focal point (0.30). Next

determine the directrix equation and sketch the graph!

Answer :

The peak (a, b) is (1, -3)

The focus of F(a-p, b) is F(1 – 1, -3) = F(0,-3)

So the parabola opens to the left. The form of the equation of this parabola is ….

2
( − ) = −4 ( – )  ( − (−3)) 2 = −4 (1) ( – 1)

2
 ( + 3) = −4 ( – 1)
2
 – 6 + 9 = −4 – 4

2
 – 6 – 4 + 5 = 0

The directrix equation is

= +

 = 1 + 1

 = 2

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