Provide your best answer for the following math problem. Give ONLY the answer, no other words or explanation.
For example:

Answer: <most likely answer, as short as possible; not a complete sentence, just the answer!>.

The problem is: if ( 400 ) ( 7000 ) = ( 28000 ) ( 100 ^ x ) , what is the value of x ?
1
x = -3.176296326795