Question

If $x - \frac 1x = 2$, what is the value of $x^2 + \frac {1}{x^2}$ ?

• A. 4
• B. 6
• C. 2
• D. 1

Answer 1

Answer:

B. 6

$x - \frac 1x = 2$

$(x-\frac{1}{x})^2=x^2+(1/x)^2-2\times{x}\times{1/x}=2^2=4$

$x^2+(1/x)^2=4+2=6$