### Home > AC > Chapter 12 > Lesson 12.2.1 > Problem12-40

12-40.

Find the equation of $f(x)$ graphed below.

Identify all of the intercepts.

Write the equation as a factored quadratic since the two values of $x$ are known.

$y = (x − 3)(x + 1)$

Make the equation negative because the parabola opens downward.

$y=−(x−3)(x+1)$

Use a generic rectangle to multiply the factors together. Distribute the negative.