The quadratic function is .

For this function a = , so the graph opens down and the function has a maximum value.

The maximum value of the function is the y-coordinate of the vertex.

The - coordinate of the vertex is .

        (Substitute the values a = and b = 0)

0.

The y-coordinate of the vertex by evaluating the function for = 0.

     (Original function)

          ( =  0)

or 15.

The maximum value of the function is 15.

The domain is all real numbers.

The range is all real numbers less than or equal to maximum value ,or .

The function has maximum value.

The maximum value of the function is 15.

The domain is all real numbers.

The range is .