Problem 13 - Entrance Test

Simplify (a/b + b/a)^2 - (a/b - b/a)^2.

A. 0B. 2C. 4D. 2(a^2/b^2 + b^2/a^2)

Correct: C

This expression is of the form (X+Y)^2 - (X-Y)^2, which simplifies to 4XY. Here, X = a/b and Y = b/a. So, 4 * (a/b) * (b/a) = 4 * 1 = 4.