The maximum value of the function $f (x, y, z) = xyz $subject to the constraint $xy+yz+zx-a =0, a >0$ is
- $a^{3/2}$
- $\left(\dfrac{a}{3} \right) ^{3/2}$
- $\left(\dfrac{3}{a} \right) ^{3/2}$
- $\left(\dfrac{3a}{2} \right) ^{3/2}$
I am stuck on this problem. Can anyone help me please?