I am to verify that the following one-step RK3:

Phi(x, y; h) = (k1 + 4k2 + k3)/6,

k1 = f(x, y)

k2 = f(x + h/2, y + h/2 * k1)

k3 = f(x + h, y + h(-k1 + 2k2))

Is third-order.

My prof showed me how to do this, but I got overwhelmed quickly. Is there a resource, website, video, etc. that can show me how to do this sort of thing in step-by-step detail?