First. Finding the x-intercepts of
Let be the change in water level. So to find the x-intercepts of this function we can use The Rational Zero Test that states:
To find the zeros of the polynomial:
We use the Trial-and-Error Method which states that a factor of the constant term:
can be a zero of a polynomial (the x-intercepts).
So let's use an example: Suppose you have the following polynomial:
where the constant term is . The possible zeros are the factors of this term, that is:
.
Thus:
From the foregoing, we can affirm that are zeros of the polynomial.
Second. Construction a rough graph of
Given that this is a polynomial, then the function is continuous. To graph it we set the roots on the coordinate system. We take the interval:
and compute where is a real number between -2 and -1. If , the curve start rising, if not, the curve start falling. For instance:
Therefore the curve start falling and it goes up and down until and from this point it rises without a bound as shown in the figure below
