Write the equation of a parabola with a vertex at (10, 0) and a directrix x = 8.

Step-by-step explanation:

If we plot both the vertex and the directrix, we see that the parabola opens to the right.  We know this because of the fact that the directrix is a vertical line.  Because the vertex is to the right of the directrix and a parabola always opens away from the directrix, we know this is of the form

h and k are the coordinates of the vertex which we are given.  Our h = 10 and our k = 0.  P is defined as the distance between the vertex and the directrix, so our p = 2.  Filling in the equation with all of that gives us

and

and

so

Not sure what form you need it in, work form or standard form.

a 4/6 = 9/12   not proportional

step-by-step explanation:

to find which are not proportional, we can use cross products

if it is true, they are proportional.   if it is not true, they are not proportional.

a 4/6 = 9/12

4* 12 = 6*9

48 = 54

not this is not proportional  

b 2/3 = 12/18  

2* 18 = 3 * 12

36 = 36

this is proportional

c 5/4 = 10/8  

5*8 = 4*10

40 = 40

this is proportional

d 7/5 = 35/25

7*25 = 5 * 35

175 = 175

is proportional

c

step-by-step explanation: