Question

sketch the graph of the quadratic function $h(x) = 3x^2 - 12x + 9$ on the coordinate plane, ensuring to clearly label the vertex, axis of symmetry, x-intercepts, y-intercept, and at least two other distinct points that demonstrate the parabolas shape, and indicate whether it opens upward or downward.

Explanation:

Step1: Determine the direction of opening

For a quadratic function \( h(x)=ax^{2}+bx + c \), if \( a>0 \), the parabola opens upward; if \( a < 0 \), it opens downward. Here, \( a = 3>0 \), so the parabola opens upward.

Step2: Find the axis of symmetry

The formula for the axis of symmetry of a quadratic function \( h(x)=ax^{2}+bx + c \) is \( x=-\frac{b}{2a} \). For \( h(x)=3x^{2}-12x + 9 \), \( a = 3 \), \( b=- 12 \). So \( x=-\frac{-12}{2\times3}=\frac{12}{6} = 2 \). The axis of symmetry is \( x = 2 \).

Step3: Find the vertex

The x - coordinate of the vertex is the axis of symmetry \( x = 2 \). Substitute \( x = 2 \) into \( h(x) \): \( h(2)=3\times(2)^{2}-12\times2 + 9=3\times4-24 + 9=12-24 + 9=-3 \). So the vertex is \( (2,-3) \).

Step4: Find the y - intercept

The y - intercept occurs when \( x = 0 \). Substitute \( x = 0 \) into \( h(x) \): \( h(0)=3\times(0)^{2}-12\times0 + 9=9 \). So the y - intercept is \( (0,9) \).

Step5: Find the x - intercepts

Set \( h(x)=0 \), so \( 3x^{2}-12x + 9 = 0 \). Divide both sides by 3: \( x^{2}-4x + 3=0 \). Factor the quadratic: \( (x - 1)(x - 3)=0 \). Set each factor equal to zero: \( x-1 = 0\) or \( x - 3=0 \). So \( x = 1 \) or \( x = 3 \). The x - intercepts are \( (1,0) \) and \( (3,0) \).

Step6: Find other points

Let's choose \( x=4 \). Substitute \( x = 4 \) into \( h(x) \): \( h(4)=3\times(4)^{2}-12\times4 + 9=3\times16-48 + 9=48-48 + 9=9 \). So the point is \( (4,9) \). Let's choose \( x=-1 \). Substitute \( x=-1 \) into \( h(x) \): \( h(-1)=3\times(-1)^{2}-12\times(-1)+9=3 + 12+9=24 \). So the point is \( (-1,24) \).

To sketch the graph:

1. Plot the vertex \( (2,-3) \), the axis of symmetry \( x = 2 \) (a vertical line through \( x = 2 \)), the x - intercepts \( (1,0) \) and \( (3,0) \), the y - intercept \( (0,9) \), and the other points \( (4,9) \) and \( (-1,24) \).
2. Since \( a = 3>0 \), draw a parabola opening upward passing through these points.

Answer:

• Direction of opening: Upward
• Axis of symmetry: \( x = 2 \)
• Vertex: \( (2,-3) \)
• x - intercepts: \( (1,0) \), \( (3,0) \)
• y - intercept: \( (0,9) \)
• Other points: \( (4,9) \), \( (-1,24) \) (and the graph is a parabola opening upward with the above - mentioned features plotted)