Question

If $x ^ 2 + 1 / x ^ 2 = 79$ find the value of $x + 1 / x$

• A. 10
• B. 9
• C. 8
• D. 7

Answer 1

Answer:

B. 9

$(x+1/x)^2=x^2+1/x^2+2$

$(x+1/x)^2=79+2$

$(x+1/x)^2=81$

$x+1/x=\sqrt{81}=9$