Question

Qual valor da expressão
(xy-1) (elevado )2 - (1+ xy).(1-xy) + 2 xy

Answer 1

(xy-1)²=(xy)²-2.xy.1+1²=x²y²-2xy+1
(1+ xy).(1-xy)=1²-(xy)²=1-x²y²

(xy-1)² - (1+ xy).(1-xy) + 2 xy =
=x²y²-2xy+1-(1-x²y²)+2xy
=x²y²-2xy+1-1+x²y²+2xy
=2x²y²