What is an equation for the parabola with focus (0, -12) and directrix y = 12

Given:

Focus of a parabola is (0, -12) and directrix is y = 12.

To find:

The equation of the parabola.

Solution:

General form of a parabola is

      ...(i)

where, (h,k) is vertex, (h,k+p) is focus and y=k-p is directrix.

Focus is (0, -12).

        ...(ii)

Directrix is y = 12.

     ...(iii)

Adding (ii) and (iii), we get

Putting k=0 in (ii), we get

Putting h=0, k=0 and p=-12 in (i).

Therefore, the required equation of parabola is .

let m = monomial

let t = trinomial

so, m times t = t.

monomial times a trinomial = another trinomial.

step-by-step explanation: so we look at the formula un = a + (n-1)d

un is the amount of seats

n is the nth term aka row number

a is the original sequence/row number

d is the difference between each term

so in this a=22 d=6 and n can remain as n because we are simply formjng a rule

lets put these in the equation

un=22+(n-1)(6)

this is your answer to part a

however

lets double check that this is correct, we'll try putting it into the second term

un=a+(n-1)d

u2=22+(2-1)(6)

u2=22+6

u2=28

as the question said the second row has 28 seats so now we know the formula we made is correct.

as for part b

un=a+(n-1)

its asking us to find a row with 100 seats.

remember un was the amount of seata so all we do is substitute this in.

un=100 a=22 d=6

un=a+(n-1)d

100=22+(n-1)(6)

so now we simplify to find n which is the row number.

100-22=22+(n-1)(6)-22

78=(n-1)(6)

78/6=(n-1)(6)/6

13=n-1

13+1=n-1+1

14=n

so now we know that in the 14th row there is 100 seats.

hope this and that you understood! its my first time using the app or anyone out on here : p its also me to revise so a bunch! ask more questions if you dont understand ☺