Question

Match the equations representing parabolas with their directrixes. y + 8 = 3(x + 2)2 y − 14 = -(x − 3)2 y + 7.5 = 2(x + 2.5)2 y − 17 = -(x − 3)2 y + 7 = (x − 4)2 y − 6 = -(x − 1)2 Directrix Equation of Parabola y = -7.25 arrowRight y = 6.25 arrowRight y = 17.25 arrowRight y = 14.25 arrowRight

Answer 1

Answer:

Part 1) $y+8=3(x+2)^{2}$ -----> $y=-8.08$

Part 2) $y-14=-(x-3)^{2}$ ---->  $y=14.25$

Part 3) $y+7.5=2(x+2.5)^{2}$ ---->  $y=-7.625$

Part 4) $y-17=-(x-3)^{2}$ -----> $y=17.25$

Part 5) $y+7=(x-4)^{2}$ ----> $y=-7.25$

Part 6) $y-6=-(x-1)^{2}$ ---->  $y=6.25$

Step-by-step explanation:

we know that

The equation of a vertical parabola in vertex form is equal to

$y-k=\frac{1}{4p}(x-h)^{2}$

where

(h,k) is the vertex

The directrix is

$y=k-p$

case 1) we have

$y+8=3(x+2)^{2}$

the vertex is the point (-2,-8)  

$\frac{1}{4p}=3$

$p=\frac{1}{12}$

The directrix is equal to

$y=-8-\frac{1}{12}=-8.08$

case 2) we have

$y-14=-(x-3)^{2}$

the vertex is the point (3,14)  

$\frac{1}{4p}=-1$

$p=-\frac{1}{4}$

The directrix is equal to

$y=14+\frac{1}{4}=14.25$

case 3) we have

$y+7.5=2(x+2.5)^{2}$

the vertex is the point (-2.5,-7.5)    

$\frac{1}{4p}=2$

$p=\frac{1}{8}$    

The directrix is equal to

$y=-7.5-\frac{1}{8}=-7.625$

case 4) we have

$y-17=-(x-3)^{2}$

the vertex is the point (3,17)      

$\frac{1}{4p}=-1$

$p=-\frac{1}{4}$    

The directrix is equal to

$y=17+\frac{1}{4}=17.25$

case 5) we have

$y+7=(x-4)^{2}$

the vertex is the point (4,-7)      

$\frac{1}{4p}=1$

$p=\frac{1}{4}$    

The directrix is equal to

$y=-7-\frac{1}{4}=-7.25$

case 6) we have

$y-6=-(x-1)^{2}$

the vertex is the point (1,6)      

$\frac{1}{4p}=-1$

$p=-\frac{1}{4}$    

The directrix is equal to

$y=6+\frac{1}{4}=6.25$