Derive the equation of the parabola with a focus at (0, −4) and a directrix of y = 4.
A.f(x) = −16x2
B.f(x) = 16x2
C.f(x) = −one sixteenth x2
D.f(x) = one sixteenthx2

Question

Derive the equation of the parabola with a focus at (0, −4) and a directrix of y = 4.
A.f(x) = −16x2
B.f(x) = 16x2
C.f(x) = −one sixteenth x2
D.f(x) = one sixteenthx2

anonymous · Answer

@random231 @aaronq @sourwing @princeharryyy @satellite73 @DarkMoonZ @Baby_Bear69

welshfella · Answer

the general form is  x^2 = 4ay  where a = the y coordinate of the focus 

can you work it out ?

anonymous · Answer

what do i work out sorry i have no idea what to do with these types of questions

welshfella · Answer

the focus is at (0,-4)  - that is the y coordinate is - 4

welshfella · Answer

x^2 = 4(-4)y

welshfella · Answer

this type of parabola as the origin at (0,0)    because x = 0 when y = 0 and as the focus is  negative 4 opens downwards

anonymous · Answer

so x^2=16y?

welshfella · Answer

|dw:1439568914238:dw|