Final answer:
To find the smallest poster area with a fixed printed area of 388 square centimeters, calculate optimized values for the width and height of the printed area, considering the margins, and derive the poster's dimensions by adding the margins to these values.
Step-by-step explanation:
To find the dimensions of the poster with the smallest area given a fixed printed area, we should first determine the dimensions of the printed area. We know that the printed area is 388 square centimeters and that the margins do not change. Let's denote the width of the printed area as w and the height as h.
The area of the printed material is given by Area = w × h = 388 cm². The total width of the poster would be w + 2×(8 cm) (since there are two side margins), and the total height would be h + 2×(4 cm) (since there are top and bottom margins).
To minimize the area of the poster, we need to minimize the function for the total area of the poster A(w,h) = (w + 16)(h + 8). As the printed area is fixed, we can express h in terms of w using h = 388/w and substitute this into the function to get A(w) = (w + 16)((388/w) + 8).
Taking the derivative dA/dw and setting it to zero, we find the optimal value for w, and consequently, we calculate h. The dimensions of the poster that minimize the total area can then be determined by adding the margins to these optimized values of w and h.