The expression you're asking to simplify is $-7\sqrt{48}$.

Here's how we simplify it:

1. Break down $\sqrt{48}$ into its prime factors: $\sqrt{48} = \sqrt{16 \times 3} = \sqrt{16} \times \sqrt{3} = 4\sqrt{3}.$

2. Now substitute this back into the expression: $-7\sqrt{48} = -7 \times 4\sqrt{3} = -28\sqrt{3}.$

So, the simplified form of $-7\sqrt{48}$ is $-28\sqrt{3}$.

Would you like further clarification or additional details on this? Here are a few related questions you might find useful:

1. How do you simplify square roots with larger numbers?
2. What are the properties of square roots that help in simplification?
3. How do you handle negative square roots in expressions?
4. Can square roots be simplified if the number is a perfect square?
5. How do you simplify expressions with cube roots instead of square roots?

Tip: Always look for perfect square factors when simplifying square roots, as it makes the process much easier!