d(- 0.00000003*X6 0.00001*X5 - 0.0018*X4 0.1576*X3 - 7.5998*X2 201.2044*x - 2048.025)/dx = 0
The expression, as written, appears to be the derivative of a 6th degree polynomial function. An example of Such a function is:
f(x) = 1.2x^6 + 7x^5 - x^4 + dx^3 - 0.414x^2 + 4x + 5
For simplicity, I have underscored each of the 7 terms given. The important thing to notice here is that every pair of consecutive terms is combined by way of + or - (e.g., 7x^5 - x^4 , 4x + 5 , etc.).
But your expression has no operation between - 0.00000003*X6 and 0.00001*X5, nor between 0.0018*X4 and 0.1576*X3.
I suggest that you should recheck the problem as was presented to you, looking for the missing operation signs as discussed above.