If xy = 1, which is equivalent to x(x – 1)(y + 1)?

Question

If xy = 1, which is equivalent to x(x – 1)(y + 1)?

A. x – 1

B. x2 – 1

C. x2 – x

D. x2 – x + y – 1

I don't understand this question.

Answer 1

Multiply the factors and replace xy with 1

x(x-1)(y+1) = x(xy-y+x-1) = x(1-y+x-1) = x(-y+x) = -xy+x² = -1+x² = x²-1