a^2-b^2 (a-b)(a+b)is divisible by a-b

a^3-b^3 (a-b)(a^2+ab+b^2)is divisible by a-b

similarly a^4-b^4 is also divisible by a-b

it can be thus shown that a^n-b^n is always divisble by a-b for natural number n

 

thus a^1992-b^1992/a-b is an integer

similarly the other two

so int+int+int which is also an integer