Question

If $x^2+\frac{1}{x^2}=79$, then $x+\frac{1}{x}=$________

• A. $\sqrt{75}$
• B. $9$
• C. $\sqrt{79}$
• D. none of these

Answer 1

Answer: (B)

$9$

$x^2+\frac{1}{x^2}=79$

$(x+\frac{1}{x}{)}^2=x^2+\frac{1}{x^2}+2$

$(x+\frac{1}{x}{)}^2=79+2$

$(x+\frac{1}{x}{)}^2=81$

$x+\frac{1}{x}=9$