Question

若xy=根号2，x-y=5倍的根号2-1，则（x+1）（y-1）=多少

今天踩了一下午的排，累死了，现在脑子不好使，就想睡觉。
哪个天才来帮帮我

Answer 1

(x+1)(y-1)
= xy-x+y-1
= xy-(x-y)-1
= 根号2 - (5倍的根号2-1) - 1
= 根号2 - 5倍的根号2 +1 - 1
= - 4倍的根号2

Answer 2

xy=√2，x-y=5√2-1，
则（x+1）（y-1）=xy-x+y-1=xy-（x-y）-1=√2-（5√2-1）-1=-4√2

Answer 3

=-4倍根2

Answer 4

i am wery like chocolate.