∫f(x)g′′(x)−f′′(x)g(x)dx is equal to
f(x)g′(x)
f′(x)g(x)−f(x)g′(x)
f(x)g′(x)−f′(x)g(x)
f(x)g′(x)+f′(x)g(x)
∫f(x)g′′(x)−f′′g(x)dx=∫f(x)g′′(x)dx−∫f′′(x)g(x)dx=f(x)g′(x)−∫f′(x)g′(x)dx−g(x)f′(x)−∫g′(x)f′(x)dx=f(x)g′(x)−f′(x)g(x)