Final answer:
The concept that best explains the impact of one poorly maintained house in a neighborhood is external obsolescence. External obsolescence refers to factors outside a property that negatively affect its value.
Step-by-step explanation:
The concept that best explains the impact of one poorly maintained house in a large neighborhood is External obsolescence. External obsolescence refers to factors outside a property that negatively affect its value. In this case, the poorly maintained house stands out compared to the others, and its poor condition can result in lower property values, a negative perception of the neighborhood, and potential disinvestment from other homeowners.