Final answer:
The function F(x) = 14 - x^2 is not defined as a real number when x is less than 0.
Step-by-step explanation:
The function F(x) = 14 - x^2 is not defined as a real number when the expression under the square root, x^2, is negative. To find the values of x for which the function is not defined, we set x^2 < 0 and solve for x:
x^2 < 0
x < 0
Therefore, the function F(x) = 14 - x^2 is not defined as a real number for any value of x that is less than 0.