Mathematics
If y is the mean proportional between x and z, prove that
xyz(x + y + z)3 = (xy + yz + zx)3
Answer
Given, y is the mean proportional between x and z then,
y2 = xz [….Eq 1]
Given, xyz(x + y + z)3 = (xy + yz + zx)3
Solving L.H.S. first,
xyz(x + y + z)3
= xz.y(x + y + z)3
Putting value of xz as y2 from equation 1:
= y2.y(x + y + z)3
= y3(x + y + z)3
= (y(x + y + z))3
= (xy + y2 + yz)3
= (xy + xz + yz)3 = R.H.S.
L.H.S. = R.H.S. , hence proved, xyz(x + y + z)3 = (xy + yz + zx)3.