1. The problem is to rewrite the expression $6 - \sqrt{-8}$ as a complex number and simplify all radicals. 2. Recall that the imaginary unit $i$ is defined as $i = \sqrt{-1}$. 3. We can rewrite $\sqrt{-8}$ as $\sqrt{8 \times -1} = \sqrt{8} \times \sqrt{-1} = \sqrt{8} \times i$. 4. Simplify $\sqrt{8}$: since $8 = 4 \times 2$, we have $\sqrt{8} = \sqrt{4 \times 2} = \sqrt{4} \times \sqrt{2} = 2\sqrt{2}$. 5. Substitute back: $\sqrt{-8} = 2\sqrt{2}i$. 6. Therefore, the expression becomes $6 - 2\sqrt{2}i$. 7. This is the complex number form with the real part $6$ and the imaginary part $-2\sqrt{2}i$. Final answer: $$6 - 2\sqrt{2}i$$