Question

If $\underset{x\to a}{lim}\frac{x^5-a^5}{x-a}=80$ then the value of $a$ is

• A. $4$
• B. $2$
• C. $3$
• D. $5$

Answer 1

The correct option is B $2$

Given,

$\underset{x\to a}{lim}\frac{x^5-a^5}{x-a}=80$

or, $5a^4=80$ [ Using direct formula]

or, $a^4=16$

or, $a=2$.