The quadratic polynomial is commonly used to relate two variables, y and x, such that the relationship is nonlinear. An oceanographer measures light depth penetration in an estuary (y, microamps

× 103)

at depths (x, inches) and computes the following polynomial: y = 0.05x2 − 0.35x + 0.7. Graph light penetration versus depth over the range from 1 to 4 in. When the water is polluted, the equation is y = 0.05x2 – 0.36x + 0.65. On the same graph, plot the equation for polluted water and discuss the difference in the two graphs.