Which spheres are involved when sedimentary rocks form from parts of sea shells at the bottom of the ocean?

It is the interaction between the lithosphere and the hydrosphere

Explanation:

Lithosphere represents the crustal and a small portion of the upper mantle whereas hydrosphere is the region that contains all the water bodies on earth, in the form of ice, liquid, and vapor.

The ocean is rich in numerous marine species. These species when they die their hard parts are deposited at the bottom of the ocean. These include the shells of brachiopods, gastropods, and cephalopods. Near the ocean floor, the pressure is extremely high and oxygen is relatively low in comparison to the amount that is present in the atmosphere. So it provides these shells the necessary conditions for preservation. With the further deposition of sediments over them, they get buried and undergoes compaction due to the overlying sediments. In due course of time, it forms a sedimentary rock such as shale, sandstone, and limestone and is rich in these fossilized shells.

Thus the entire process takes place due to the interaction between the lithosphere and the hydrosphere.

i assume you mean  3x^2 + 16y = 0

so y =  -3/16 x^2

The vertex is at the origin (0,0)  answer

x^2 = -16/3 y

compare with standard form x^2 = 4ay:-

the focus y coordinate of the  a =  -16/3  / 4

= -16/12 =  -4/3   so the focus is (0, -4/3) answer

and the directrix is y = 4/3  answer