Final answer:
To make the equation f(x) = x² - 9 open down, multiply the equation by -1 to reflect it along the x-axis. The new equation is f(x) = -x² + 9.
Step-by-step explanation:
To make the equation f(x) = x² - 9 open down, we need to reflect it along the x-axis. This can be done by multiplying the equation by a negative number. Let's multiply the equation by -1 to make it open down.
So the new equation is:
f(x) = -x² + 9
In this new equation, the graph of the function will open downward instead of upward.