Let's analyze and solve the problem in the uploaded image.

The question asks to simplify and express the given expression $7 + \sqrt{-25}$ as a complex number using $i$, if necessary.

Solution:

1. Simplify the square root of a negative number: Recall that $\sqrt{-x} = i\sqrt{x}$, where $i$ is the imaginary unit defined by $i^2 = -1$.

   $\sqrt{-25} = i\sqrt{25} = 5i$

2. Rewrite the expression: Substitute $\sqrt{-25}$ with $5i$ in the given expression: $7 + \sqrt{-25} = 7 + 5i$

3. Final Answer: The simplified form is: $\boxed{7 + 5i}$

So, the real part is 7, and the imaginary part is 5.

Let me know if you would like a further explanation!

Related Questions:

1. How do you simplify square roots of other negative numbers, such as $\sqrt{-16}$ or $\sqrt{-49}$?
2. What is the definition of a complex number, and how is it represented on a plane?
3. Why is $i^2 = -1$, and how does it relate to complex numbers?
4. Can complex numbers be added, subtracted, or multiplied like real numbers? How?
5. What are the applications of complex numbers in engineering or physics?

Tip:

When working with square roots of negative numbers, always separate the negative sign first to rewrite the square root in terms of $i$.