Question

The function f(x) = –x2 – 4x + 5 is shown on the graph.

On a coordinate plane, a parabola opens down. It goes through (negative 5, 0), has a vertex at (negative 2, 9), and goes through (1, 0).
Which statement about the function is true?

The domain of the function is all real numbers less than or equal to −2.
The domain of the function is all real numbers less than or equal to 9.
The range of the function is all real numbers less than or equal to −2.
The range of the function is all real numbers less than or equal to 9.

does anyone know the answer??

Answer 1

Answer: The range of the function is all real numbers less than or equal to 9.

Explanation:

Recall that a parabola represents a quadratic function, which is a polynomial function of degree 2. Then, recall that the domain of any polynomial function must comprise of all real numbers. Hence, the domain of the quadratic function represented by the parabola is all real numbers. So, the first and second statements are false.

Since the parabola opens down, then its vertex (-2,9) is a maximum point. This indicates that the y-coordinate of the uppermost point on the parabola is y=9.

So, the y-coordinates of all points on the parabola must be at most 9, or equivalently are less than or equal to 9. Therefore, the range of the function (i.e. set of y-coordinates of all points on the parabola) is all real numbers less than or equal to 9. This indicates that the third statement is false, while the last statement is true.