To find the equation of the axis of symmetry and the coordinates of the vertex for the quadratic function \( y = x^2 - 4x - 9 \), we can use the following formulas:
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The equation of the axis of symmetry for a quadratic function in the form \( y = ax^2 + bx + c \) is given by: \[ x = -\frac{b}{2a} \] where \( a = 1 \) and \( b = -4 \) in this case.
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The coordinates of the vertex can be found using the same value of \( x \) obtained from the axis of symmetry and then plugging it back into the function to find the corresponding \( y \) value.
Step 1: Find the axis of symmetry
Given:
- \( a = 1 \)
- \( b = -4 \)
Calculate \( x \): \[ x = -\frac{-4}{2 \times 1} = \frac{4}{2} = 2 \]
Thus, the equation of the axis of symmetry is: \[ \boxed{x = 2} \]
Step 2: Find the coordinates of the vertex
Now that we have the \( x \)-coordinate of the vertex, we can find the \( y \)-coordinate by substituting \( x = 2 \) back into the function: \[ y = (2)^2 - 4(2) - 9 \] \[ y = 4 - 8 - 9 \] \[ y = -13 \]
Therefore, the coordinates of the vertex are: \[ \boxed{(2, -13)} \]
In conclusion, the equation of the axis of symmetry is \( x = 2 \) and the coordinates of the vertex are \( (2, -13) \).