To solve the expression \((2.5 + \sqrt{-36}) - (\sqrt{7} - \sqrt{-4})\), we need to simplify each part step by step.
Step 1: Simplify \(\sqrt{-36}\)
The square root of a negative number can be expressed using the imaginary unit \(i\). \[ \sqrt{-36} = \sqrt{36} \cdot \sqrt{-1} = 6i \]
Step 2: Simplify \(\sqrt{-4}\)
Similarly, we simplify \(\sqrt{-4}\): \[ \sqrt{-4} = \sqrt{4} \cdot \sqrt{-1} = 2i \]
Step 3: Rewrite the expression using these simplifications
Now we can rewrite the original expression: \[ (2.5 + 6i) - (\sqrt{7} - 2i) \]
Step 4: Distribute the negative sign through
Next, we distribute the negative sign in the second part: \[ (2.5 + 6i) - \sqrt{7} + 2i \] This gives us: \[ 2.5 - \sqrt{7} + 6i + 2i \]
Step 5: Combine like terms
Now we combine the real parts and the imaginary parts:
- Real part: \(2.5 - \sqrt{7}\)
- Imaginary part: \(6i + 2i = 8i\)
Final Result
Putting it all together, we get: \[ (2.5 - \sqrt{7}) + 8i \]
Thus, the final result in the form \(a + bi\) is: \[ \boxed{(2.5 - \sqrt{7}) + 8i} \]