Home
Class 11
MATHS
Statement-1: The function f:R to R defin...

Statement-1: The function `f:R to R` defined by `f(x)=x^(3)+4x-5` is a bijection.
Statement-2: Every odd degree has at least one real root.

A

1

B

2

C

3

D

4

Text Solution

AI Generated Solution

The correct Answer is:
To solve the problem, we need to analyze the statements given regarding the function \( f(x) = x^3 + 4x - 5 \). ### Step 1: Determine if \( f(x) \) is a bijection A function is a bijection if it is both injective (one-to-one) and surjective (onto). #### Injectivity: To check if \( f(x) \) is injective, we need to see if \( f(x_1) = f(x_2) \) implies \( x_1 = x_2 \). Assume \( f(x_1) = f(x_2) \): \[ x_1^3 + 4x_1 - 5 = x_2^3 + 4x_2 - 5 \] This simplifies to: \[ x_1^3 - x_2^3 + 4(x_1 - x_2) = 0 \] Factoring gives: \[ (x_1 - x_2)(x_1^2 + x_1x_2 + x_2^2 + 4) = 0 \] This implies either \( x_1 - x_2 = 0 \) (which means \( x_1 = x_2 \)) or \( x_1^2 + x_1x_2 + x_2^2 + 4 = 0 \). The term \( x_1^2 + x_1x_2 + x_2^2 + 4 \) is always positive since \( x_1^2 + x_1x_2 + x_2^2 \) is non-negative (as it can be rewritten using the squares of real numbers) and adding 4 ensures it is strictly greater than 0. Thus, \( f(x) \) is injective. #### Surjectivity: Next, we check if \( f(x) \) is surjective. Since \( f(x) \) is a polynomial of odd degree (3), it will cover all real numbers as \( x \) approaches \( \pm \infty \). Therefore, \( f(x) \) is surjective. Since \( f(x) \) is both injective and surjective, it is a bijection. ### Step 2: Verify Statement 2 Statement 2 states that every odd degree polynomial has at least one real root. Since \( f(x) \) is a cubic polynomial (odd degree), it must have at least one real root. This statement is true. ### Conclusion Both statements are true. Therefore, the answer is that both statements are valid. ### Final Answer Both Statement-1 and Statement-2 are true. ---

To solve the problem, we need to analyze the statements given regarding the function \( f(x) = x^3 + 4x - 5 \). ### Step 1: Determine if \( f(x) \) is a bijection A function is a bijection if it is both injective (one-to-one) and surjective (onto). #### Injectivity: To check if \( f(x) \) is injective, we need to see if \( f(x_1) = f(x_2) \) implies \( x_1 = x_2 \). ...
Promotional Banner

Similar Questions

Explore conceptually related problems

The function f: R to R defined by f(x) = 4x + 7 is

the function f:R rarr R defined as f(x)=x^(3) is

The function f:R rarr R is defined by f(x)=3^(-x)

The function f:R rarr R defined as f(x) = x^3 is:

Show that the function f:R rarr R given by f(x)=x^(3)+x is a bijection.

Show that f:R rarr R, defined as f(x)=x^(3) is a bijection.

The function f:R rarr R is defined by f(x)=(x-1)(x-2)(x-3) is

Show that the function f:R rarr R defined by f(x)=3x^(3)+5 for all x in R is a bijection.

Show that the function f:R rarr R defined by f(x)=3x^(3)+5 for all x in R is a bijection.

Consider a function f:R rarr R defined by f(x)=x^(3)+4x+5 , then