If x,y,zx, y, zx,y,z are in geometric progression and x+y+z=kx+y+z = kx+y+z=k, x2+y2+z2=mx^2+y^2+z^2=mx2+y2+z2=m, express xy+yz+zxxy+yz+zxxy+yz+zx in terms of kkk and mmm.
k2−m2\frac{k^2-m}{2}2k2−m
k2−mk^2-mk2−m
k2+m2\frac{k^2+m}{2}2k2+m
m−k2m-k^2m−k2