Question

$x^{11}-\frac1{x^{11}}=2\sqrt{15}$ആയാൽ $x^{11}+\frac1{x^{11}}$എത്ര?

• A. 6
• B. 8
• C. 16
• D. 12

Answer 1

Answer:

B. 8

$x^{11}-1/x^{11}=K$

$\because(a+b)^2=(a-b)^2+4ab$

$\implies{x^{11}+1/x^{11}}=\sqrt{K^2+4}$

$=\sqrt{({2\sqrt{15})^2+4}}$

$=\sqrt{60+4}=\sqrt{64}=8$