The interval of the decreasing function f(x)=x3-x2-x-4
13,1
-13,1
-13,13
-1,-13
Explanation for correct option:
Find the interval:
Given function is f(x)=x3-x2-x-4
We know that a function f(x) is decreasing when dfxdx<0
Therefore,
⇒ddxx3-x2-x-4<0⇒3x2-2x-1<0⇒3x2-3x+x-1<0⇒3xx-1+x-1<0⇒x-13x+1<0
⇒x∈-13,1
Hence, the correct answer is option (B).
Find the intervals in which the function f given byis
(i) increasing (ii) decreasing