Really big numbers that can easily be estimated.
like
9,998 - 2,999
Answer:
f(5)=(5)²=25
f(-5)=(-5)²=25
NB. Some teachers don't want 2 equals on one line, if it's your case please don't write the 2 equals on the same line
X>-2.That's the solution.
The answer to this problem is

When taking square roots, you can't take square roots of negative roots of negative numbers. So, what will work for the domain of u(x) is what makes u(x) zero or more. We can make an inequality for that.
u(x) ≥ 0.

9x + 27 ≥ 0 by squaring both sides
9x ≥ -27
x ≥ -3
So the domain of the function is when x ≥ -3 is true.