Please show step by step of working out the value of r for which is A is aminimum and calculate the minimum surface area of the container. The total surface area, of each container is modelled by function A= πr^2+1000/r.

(remember to use the derivative to show you have found the minimum)

The minimum surface area of the container is 276.791 square units.

Step-by-step explanation:

Let be , , . The first and second derivatives of such function are, respectively:

First derivative

Second derivative

The critical values of are determined by equalizing first derivative to zero and solving it: (First Derivative Test)

(since radius is a positive variable)

To determine if critical value leads to an absolute minimum, this input must be checked in the second derivative expression: ()

The critical value leads to an absolute minimum, since value of the second derivative is positive.

Finally, the minimum surface area of the container is:

The minimum surface area of the container is 276.791 square units.

walter needs to make at least 5 more cookies but no more than 40. 5 ≤ x ≤ 40

step-by-step explanation:

20 ≤ x + 15 ≤ 55

subtract 15 from all parts

20-15 ≤ x + 15-15 ≤ 55-15

5 ≤ x ≤ 40

this means how many more cookies he has to make

walter needs to make at least 5 more cookies, but no more than 40 cookies; 5 ≤ x ≤ 40