Question

If $\underset{x\to -a}{lim}\frac{x^7+a^7}{x+a}=7$
then the value of a is

• A. 1
• B. -1
• C. 7
• D. none of these

Answer 1

Answer: (A), (B)

The correct options are
A 1
B -1

$\underset{x\to -a}{lim}\frac{x^7+a^7}{x+a}=7$

$\Rightarrow \underset{x\to -a}{lim}\frac{7x^6}{1}=7$

$\Rightarrow 7a^6=7\Rightarrow a=\pm 1$