Question

if xy+yz+zx= -1 then find value of xy-yz-zx

Answer 1

xy + yz + zx= -1
xy = -1 -yz -zx
xy+1= -yz -zx ,let us taken as ............eq(1)
given ,
xy - yz -zx = ???
by substituting eq(1)
>xy+xy +1
>2xy +1
therefore,answer is 2xy +1

Answer 2

xy+yz+zx=-1
yz+zx=-1-xy
Then,xy-yz-zx=xy+1+xy
=2x+1