A scientist wants to compare the behavior of dolphins in a part of the Gulf of Mexico contaminated by an oil spill to the behavior of dolphins in a part of the Gulf of Mexico not affected by the oil spill. Which of the following is the best description of the research design for this study?

Observational study

Step-by-step explanation:

In a sample survey, participants answer a survey or questionnaire.

In an observational study, a sample is only observed without any manipulation.

In an experiment, random samples are selected.  One sample is then given an experimental treatment, and the effects (if any) are measured.

In this case, the scientist is not randomly selecting his samples, controlling the variables, or directly manipulating the dolphins' environment.  He is only observing the behavior of two different groups.  So this is an observational study.

if the eqn of the parabola is f(x) = (x-4)(x+2), we need to mult. this out to find the coordinates of the vertex.

then f(x) = x^2 + 2x - 4x - 8, and f(x) = x^2 - 2x - 8.

one way in which you can find the vertex is to calculate x = -b / (2a).   here, that comes to

        )

x = = 1.   f(1) = 1^2 - 2(1) - 8 = - 9.   vertex is at (1, -9).

        2(1) 

find another point on the curve:   let x=0, for which y=-8.   then (0, -8) is on the curve.   plot the vertex and this point and draw a smooth parabola thru both.

hope this