Question

if x + y+z=0 then (x+y)(y+z)(z+x)

Answer 1

if x + y+z=0 then (x+y)(y+z)(z+x) is automatically 0 as x=0, y=0 and z=0 then only we will get the sum zero 0+0+0=0
now (x+y)(y+z)(z+x) = (0+0)(0+0)(0+0)=0

so the answer is 0

Hope it helped.....