Question:

Consider the following statements in respect of the function $f(x)=x^{3}-1, x \in[-1,1]$ I. $f(x)$ is increasing in $[-1,1]$ II. $f(x)$ has no root in $(-1,1)$. Which of the statements given above is/are correct?

Updated On: Mar 18, 2024
  • Only I
  • Only II
  • Both I and II
  • Neither I nor II
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The Correct Option is A

Solution and Explanation

Since $f (x)$ is an increasing function in $[- 1, 1]$ and it has a root in $(- 1, 1)$.
$\therefore$ Only statement I is correct.
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Concepts Used:

Increasing and Decreasing Functions

Increasing Function:

On an interval I, a function f(x) is said to be increasing, if for any two numbers x and y in I such that x < y, 

⇒ f(x) ≤ f(y)

Decreasing Function:

On an interval I, a function f(x) is said to be decreasing, if for any two numbers x and y in I such that x < y,

⇒ f(x) ≥ f(y)

Strictly Increasing Function:

On an interval I, a function f(x) is said to be strictly increasing, if for any two numbers x and y in I such that x < y,

⇒ f(x) < f(y)

Strictly Decreasing Function:

On an interval I, a function f(x) is said to be strictly decreasing, if for any two numbers x and y in I such that x < y,

⇒ f(x) > f(y)

Graphical Representation of Increasing and Decreasing Functions