Answer:
The length of DB is 8
Step-by-step explanation:
I know it doesn't look EXACTLY like the one in the diagram but I just followed the measurements provided
That is the vertex form of a quadratic equation
I believe it is 8x.
Use the formula A=1/2(b*h)
A=1/2(4x(5x-1))
A=1/2(20x-4x)
A=1/2(16x)
A=8x