Question

證明下列不等式:
(1)若x，y，z∈R，a，b，c∈R⁺，則z²≥2(xy+yz+zx)
(2)若x，y，z∈R⁺，且x+y+z=xyz，則≥2()

Answer 1

證明略

∵上式顯然成立，∴原不等式得證。