It's just 0. So once again, this is just going to be equal to 2x. In general, the derivative with respect to x of x squared plus any constant is going to be equal to 2x. The derivative of x squared with respect to x is 2x. The derivative of a constant with respect to x, a constant does not change with respect to x, so it's just equal to 0. You apply the derivative operator to any of these expressions, and you get 2x. Now let's go the other way around.