To rewrite the function \( f(x) = x^2 + 12x - 69 \) by completing the square, follow these steps:
- Start with the quadratic part of the function, which is \( x^2 + 12x \).
- To complete the square, take the coefficient of \( x \) (which is 12), divide it by 2, and square the result: \[ \left(\frac{12}{2}\right)^2 = 6^2 = 36 \]
- Rewrite the quadratic expression by adding and subtracting this square: \[ x^2 + 12x = (x^2 + 12x + 36) - 36 = (x + 6)^2 - 36 \]
- Substitute this back into \( f(x) \): \[ f(x) = (x + 6)^2 - 36 - 69 \]
- Combine the constant terms: \[ -36 - 69 = -105 \]
- Thus, the function can be rewritten as: \[ f(x) = (x + 6)^2 - 105 \]
So the final answer is: \[ f(x) = (x + 6)^2 - 105 \]