3)

Step 1:

Let the two non negative numbers be and .

The sum of two numbers is .

.

.

Product of one number and square of other number is .

.

The product of the two numbers is maximum, find the two number equating its second derivative to zero.

So .

Therefore the two non negative numbers are and .

Step 2:

Given product of one number and square of other number is maximum.

The product of these two numbers is 108.

Solution:

Therefore the two non negative numbers are and .

The product  is 108.

4)

Step 1:

The function is and point is .

Plot the graph of given function .

Graph:

Graph the function .

Now observe the graph :

The points of a function that are closer to point are .

Solution:

The points closest to the point are .