And to think about that, we have to find its second derivative. So let's write g of x over here. We know g of x is equal to two x plus the definite integral from zero to x of f of t dt. We've already taken its derivative, but we'll do it again. G prime of x is equal to two plus fundamental theorem of calculus, the derivative of this right over here is just f of x. And if we have the second derivative of g, g prime prime of x, this is equal to derivative of two is just zero. And the derivative of f of x is f prime of x.