已知：实数x，y，z满足
x/(y+z)+y/(x+z)+z/(x+y)=1

求：x2/(y+z)+y2/(x+z)+z2/(x+y)=?

x+y+z
=(x+y+z)*[x/(y+z)+y/(x+z)+z/(x+y)]
=x+y+z+x2/(y+z)+y2/(x+z)+z2/(x+y)

∴ x2/(y+z)+y2/(x+z)+z2/(x+y)=0