Answer:
![y^(2)=-16x](https://img.qammunity.org/2020/formulas/mathematics/middle-school/cgymtehw3ue3w0dxvafqk7vewry1knd7lj.png)
Explanation:
we know that
The equation of a horizontal parabola written in standard form is equal to
![(y-k)^(2)=4p(x-h)](https://img.qammunity.org/2020/formulas/mathematics/middle-school/ln2th6dvj4mr61kabv1hs42xuj7snljbit.png)
where
(h,k) is the vertex of the parabola
In this problem we have
![(h,k)=(0,0)](https://img.qammunity.org/2020/formulas/mathematics/middle-school/1x28ag6wt4nuh7aisn63yudowbk0wfvci2.png)
The coordinates of the focus are (h+p,k)
In this problem we have
![F(-4,0)](https://img.qammunity.org/2020/formulas/mathematics/middle-school/upnnxz6oiieufoind6aoqd45673m3lich8.png)
therefore
![p=-4](https://img.qammunity.org/2020/formulas/mathematics/middle-school/f95dahneugri7gk3tbp93mom3vbzi202rp.png)
substitute
![(y-0)^(2)=4(-4)(x-0)](https://img.qammunity.org/2020/formulas/mathematics/middle-school/gops00ubc09zoaibjg2nqbje11ca7ev895.png)
![y^(2)=-16x](https://img.qammunity.org/2020/formulas/mathematics/middle-school/cgymtehw3ue3w0dxvafqk7vewry1knd7lj.png)