What is 4a^6b^5c^4 x -7b^7c^6?

First, let's distribute the terms in the first expression:

4a^6b^5c^4 x = 4a^6b^5c^4x

Next, multiply each term by -7b^7c^6:

-7b^7c^6
= -28a^6b^12c^10

Therefore, the final result is:

4a^6b^5c^4 x -7b^7c^6 = 4a^6b^5c^4x - 28a^6b^12c^10