Give the domain of `f(x) = sqrt(-15-x)` in interval notation.    

Box 1: Enter your answer using interval notation. Example: [2,5)
Use U for union to combine intervals. Example: (-oo,2] U [4,oo)
Enter each value as a number (like 5, -3, 2.2172) or as a calculation (like 5/3, 2^3, 5+4)
Enter DNE for an empty set. Use oo to enter Infinity.