Question

The function $f(x) = x^2 - 2x$ is strictly decreasing in the interval.

• A. (-∞, -1)
• B. (-1, ∞)
• C. (-∞, 1)
• D. (1, ∞)

Answer 1

Answer: (C)

(-∞, 1)

Answer 2

$f(x) = x^2-2x$
The function $f(x) = x^2 - 2x$ is strictly decreasing if
$f'(x) < 0$
$\frac {d}{dx}(x^2-2x) < 0$
$2x-2 < 0$
$2x < 2$
$x <1$
$⇒ x ∈ (-∞, 1)$

So, the correct option is (C): $(-∞, 1)$