What is the possible size for side x ?

You are assembling pieces of an iron gate to complete a fence. the finished gate will look like the one below. in order to assemble the gate it is important to under how the pieces are related. part 1: how are pies 1 and 2 in the archway related? part 2: how are the rectangular sections 5 and 6 in the center of the gate related to each other?

If c(x) = 4x – 2 and d(x) = x2 + 5x, what is (cxd)(x)

Ineed with math stuff it involves graphs