In 1990, tests showed that water in a lake was polluted with 7 milligrams of mercury compounds per 1000 liters of water. Cleaning up the lake became an immediate priority, and environmentalists determined that the pollution level would drop at the rate of 0.75 milligrams of mercury compounds per 1000 liters of water per year if all of their recommendations were followed. If 1990 corresponds to x = 0, find the equation of the line that allows the environmentalists to predict the pollution level y in future years if their recommendations are followed. Sketch the graph of the equation and determine when the lake will be free of mercury pollution according to this graph.

Step-by-step explanation:

First, we need to make the Equation

As the rate of change in mercury compound per year is 0.75 mg per thousand liter, So

m = -0.75

Equation of the line will be as follow

y = -0.75x + c

In 1990

x = 0

Y( 0 ) = 7

Placing values in the equation

7 = -0.75 (0) + c

7 = c

Now the Equation will be as follow

y = 0.75x + 7    

Grasph is attached with this asnwer please find it.

x=-2

infinite number of lines, so there is an infinite number of equations.

step-by-step explanation:

there are an infinite number of line that passes through the point (-2,5)

x=-2   is one line that passes through the point

y = 5 is another line that passes through the point

(these two lines are perpendicular to each other).

since the number of   numbers are infinite and the slope is the ratio of two numbers,(change in y over change in x) we can have an infinite number of slopes.     our only condition is that it passes through the point (-2,5)