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 Direction of Opening

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

Step2: Find Vertex and Axis of Symmetry

The x - coordinate of the vertex (and axis of symmetry) is given by \( x=-\frac{b}{2a} \). For \( h(x)=3x^{2}-12x + 9 \), \( a = 3 \), \( b=-12 \). So \( x=-\frac{-12}{2\times3}=\frac{12}{6} = 2 \).
To find the y - coordinate of the vertex, substitute \( x = 2 \) into \( h(x) \): \( h(2)=3(2)^{2}-12(2)+9=3\times4-24 + 9=12-24 + 9=-3 \). So the vertex is \( (2,-3) \) and the axis of symmetry is \( x = 2 \).

Step3: Find y - intercept

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

Step4: Find 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 \( (3,0) \).

Step5: Find Two Other Points

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

Step6: Sketch the Graph

• Plot the vertex \( (2,-3) \), axis of symmetry \( x = 2 \), x - intercepts \( (1,0) \), \( (3,0) \), y - intercept \( (0,9) \), and the other points \( (4,9) \), \( (-1,24) \).
• Since the parabola opens upward, draw a U - shaped curve passing through these points, symmetric about \( x = 2 \).

Answer:

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