Test Index

NCERT Class XI Mathematics - Limits and Derivatives - Solutions

© examsnet.com
Question : 31 of 72
Marks: +1, -0
If the function f(x) satisfies lim⁡x→1f(x)−2x2−1\lim\limits_{x\to 1}\frac{f(x)-2}{x^2-1} = π, evaluate lim⁡x→1\lim\limits_{x\to 1} f (x).
Solution:  
We have lim⁡x→1f(x)−2x2−1\lim\limits_{x\to 1}\frac{f(x)-2}{x^2-1} = π
Since lim⁡x→1\lim\limits_{x\to 1} (x2−1)(x^2-1) = 0
∴ For lim⁡x→1\lim\limits_{x\to 1} f(x)−2x2−1\frac{f(x)-2}{x^2-1} to exist, we must have lim⁡x→1\lim\limits_{x\to 1} [f (x) - 2] = 0
[Since lim⁡x→1\lim\limits_{x\to 1} (f (x) - 2) ≠ 0, then the given limit can’t exist]
⇒ lim⁡x→1\lim\limits_{x\to 1} f (x) - 2 = 0 ⇒ $\lim↙{x→1} f (x) = 2.
© examsnet.com
Go to Question: