Determine the global extreme values of the function on the given set without using calculus.
Recall the existence of global extrema. Let f(x, y) be a continuous function on a closed, bounded domain . Then f(x, y) has both a minimum and a maximum value on .
The given domain is D = {(x, y) | x2 + y2 ≤ 5}.
This domain is . Also, f(x, y), being an exponential function, continuous.
Thus f(x, y) attain both a maximum and minimum on D.
Write
Observe that f(x, y) will attain its maximum value when attains its value. This will occur when x2 + y2 attains its value. Since x2 ≥ 0 and y2 ≥ 0, this value of x2 + y2 is x2 + y2 = .
Find the maximum value of f(x, y).
Write
Observe that f(x, y) will attain its minimum value when attains its value. This will occur when x2 + y2 attains its value. Since x2 ≥ 0 and y2 ≥ 0, this value of x2 + y2 is x2 + y2 = .
Find the minimum value of f(x, y).
A. B. C. D.