(a).

The height of projectile is given by quadratic function .

The maximum value of height occurs when the value is maximum.

The value of is maximum at .

The function is .

  and .

Substitute above values in then 

The maximum height occurs at .

(b).

The maximum height of projectile:

Substitute in the function .

The maximum height is .

(c).

The projectile will strike the water when height is zero.

Then

 substitute   and and in the above fucntion

and

The projectile will strike the water at a distance of .

(d).

Graph:

Graph of the   and .

(e).

Graph:

Graph of the   and .

Observe the graph :

The projectile will strike the water at a distance of at .

The maximum height is . at .

 (f).

The height of the projectile is .

Substitute in the function .

hen

 substitute   and and in the above fucntion.

and

The projectile is distance from the cliff.

(a)..

(b)..

(c).

(d).

(e).

(f)..