MCQ
The function $f(x) = 1 - {e^{ - {x^2}/2}}$ is
- ADecreasing for all $ x$
- BIncreasing for all $ x$
- ✓Decreasing for $x < 0$ and increasing for $x > 0$
- DIncreasing for $x < 0$ and decreasing for $x > 0$
$f'(x) = - {e^{ - {x^2}/2}}( - x) = x{e^{ - {x^2}/2}}$
For $f(x)$ to be increasing, $f'(x) > 0$
==> $x{e^{ - {x^2}/2}} > 0$
==> $x > 0$ and $f(x)$ to be decreasing for $x < 0$.
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