Draw the parabola through the vertex and the points where the x-intercepts occur.
Let's go through these steps one at a time.
Identify and Plot the x-intercepts
Recall the intercept form of a quadratic function.
y=a(x-p)(x-q)
In this form, where a ≠ 0, the x-intercepts are p and q. Let's consider the intercept form of our function.
y=-(x+5)(x-1)
⇕
y= - 1(x-( - 5))(x- 1)
We can see that a= - 1, p= - 5, and q= 1. Therefore, the x-intercepts occur at ( - 5,0) and ( 1,0).
Find and Graph the Axis of Symmetry
The axis of symmetry is halfway between (p,0) and (q,0). Since we know that p=- 5 and q=1, the axis of symmetry of our parabola is halfway between (- 5,0) and (1,0).
x=p+q/2 ⇒ x=- 5+ 1/2=- 4/2=- 2
We found that the axis of symmetry is the vertical line x=- 2.
Find and Plot the Vertex
Since the vertex lies on the axis of symmetry, its x-coordinate is - 2. To find the y-coordinate, we will substitute - 2 for x in the given equation.
The y-coordinate of the vertex is 9. Therefore, the vertex is the point (- 2,9).
Draw the Parabola
Finally, we will draw the parabola through the vertex and the x-intercepts.
We can see above that there are no restrictions on the x-variable. Furthermore, the y-variable takes values less than or equal to 9. We can write the domain and range of the function using this information.
Domain:& All real numbers
Range:& y ≤ 9
