A1. What is the absolute value of the difference of the solutions of the equation $\left(1-\left(1+x^{-2}\right)^{-1}\right)^{-1}=3.25$?
(A) -3
(B) -1
(C) 1
(D) 3
(E) 0
A1. We convert the equation to the form $x^{-2}=\frac{4}{9}$. The solutions are $\frac{3}{2}=1 \frac{1}{2}$ and $-\frac{3}{2}=-1 \frac{1}{2}$. The numbers differ by 3. The correct answer is $D$.