3.If ab = xy , then (a +b) ≠ (x+y) ,which smaller ? what will be its difference ?

     If the two numbers in the pair are widely separated, its sum will be larger  .  e.g., 8x 3 = 6x4 = 24

8 and 3 are widely separated than 6 and 4, hence the sum  8 + 3 =11 is larger than the sum 6 + 4 = 10.

Let ab = xy

(a+b)²  =  a² + b² + 2ab  or  2ab = (a+b)²  -  a² - b²  and

(x+y)²  =  x² + y² + 2xy  or  2xy = (x+y)²  - x² - y²

Invariably It satisfies the relation (a+b)²  -  a² - b²   = (x+y)²  - x² - y² or (a+b)² -  (x+y)² = a² + b² - x² - y²

If  ab = xy ,then  (a+b)²  + (x-y)² =  (a-b)²  + (x+y)²