Question

The graph of the function f(x) = (x − 3)(x + 1) is shown.

On a coordinate plane, a parabola opens up. It goes through (negative 1, 0), has a vertex at (1, negative 4), and goes through (3, 0).
Which describes all of the values for which the graph is positive and decreasing?

all real values of x where x < −1
all real values of x where x < 1
all real values of x where 1 < x < 3
all real values of x where x > 3

Answer 1

x <-1

Explanation:

The graph is positive when it is above the x axis. This is from

(- ∞, -1] U [3,+∞).

The graph is decreasing from

(-∞,1]

The graph is both positive and decreasing where x < -1