Δx (delta x) is about a secant line, a line between two points representing the rate of change between those two points. That's a "differential" (between the two points).
dx is about a tangent line to one point, representing an instantaneous rate of change. That makes it a "derivative."
Answer:
162 square inch
Step-by-step explanation:
Area = Length * Width
Area = 
The answer is B: (x-1)(x-6)(x+6)