x=y(=k/2). The maximum product is then (k^2)/4 .
If for two numbers x*y=k(=constant), then their SUM is MINIMUM if
x=y(=root(k)). The minimum sum is then 2*root(k) .
|x| + |y| >= |x+y| (|| stands for absolute value or modulus )
(Useful in solving some inequations)
Product of any two numbers = Product of their HCF and LCM .
Hence product of two numbers = LCM of the numbers if they are prime to each other