In the interval [-5, -3], the function $f(x)=(x+1)(x-3)$ is:
Answer & explanation
Correct answer: option 2
The correct answer is Option (2) → strictly decreasing
$f(x)=(x+1)(x-3)$
$f'(x)=x-3+x+1=0⇒x=2$
for $x<2$
f(x) is strictly decreasing
hence for $x∈[-5,-3]$
f(x) is strictly decreasing