What are \(a\) and \(b\) when you write \(\sqrt{\text-16}\) in the form \(a+bi\), where \(a\) and \(b\) are real numbers?

Fill in the boxes to make a true statement:
\(\displaystyle (\boxed{\phantom{30}}-3i) - (15+\boxed{\phantom{30}}i) = 7 - 12i\)

Plot each number on the real number line, or explain why the number is not on the real number line.

1. \(\sqrt{16}\)
2. \(\text- \sqrt{16}\)
3. \(\sqrt{\text-16}\)
4. \(56^{1/2}\)
5. \(\text- 56^{1/2}\)
6. \((\text-56)^{1/2}\)
    

Which expression is equivalent to \(\sqrt{\text-4}\)?