5x^3 + 7x^2 + 6x
To differentiate you take away one from the power and then multiply by it.
So if you differentiate y = x^n
you get:
dy/dx = (n-1)x^(n-1)
And the second derivative is simply the derivative of dy/dx :
So if you differentiate dy/dx you get:
d^2y/dx^2 = (n - 2)(n - 1)x^(n - 2)
So with this information you should be able to answer your question
(Hint: 6x differentiated is 6 , and 6 differentiated is 0 )