4√(-81)+6√(-36) (simplify your answer))

When looking at expressions like this,, you need to remember that the square root of a negative number does not exist in the set of Real Numbers. This means that there is no way to simplify this expression,, making the correct answer to your question Undefined.
Let me know if you have any further questions.
:)

Use photo math it it’s so good

If that's an answer