Question

If y = x3 + 3x2 + 5, what is dy/dx

Answer 1

Please, use " ^ " to denote exponentiation:  y = x^3 + 3x^2 + 5

Then the derivative of y with respect to x is  dy/dx = 3x^2 + 6x  (answer)

You could also write this result as dy/dx = 3x(x+6).

Answer 2

We need to find the derivative of that equation with respect to x.  The derivative of x^3 is 3x^2, the derivative of 3x^2 is 6x, and the derivative of any constant is always 0.  Use the power rule for derivatives that says $\frac{dy}{dx}( x^{n})=n*x ^{n-1}$.  Our derivative, then, is $3x^2+6x$.