Final answer:
To make the left side of the equation a perfect-square trinomial, add 9 to both sides.
Step-by-step explanation:
To make the left side of the equation x² - 6x - 1 a perfect-square trinomial, we need to add the square of half the coefficient of x to both sides. In this case, the coefficient of x is -6, so half of it is -3. The square of -3 is 9. Therefore, we must add 9 to both sides of the equation.
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