Calculate (123456789 X 123456789) - (123456788 X 123456790) without calculator?

Question

Working from left to right, calculate the numbers in the order shown (without using order of operation).

Replace each question mark with a mathematical sign.

Plus, minus, multiply and divide can each be used once only.

What are the highest and lowest numbers you can possibly score?

8 ? 2 ? 4 ? 7 ? 6 = ?

Answer 1

Solution = 1

Let a = 123456789

Then

a^2-((a-1)(a+1)) =
a^2-(a^2-1)=
a^2-a^2+1= 1

Answer 2

Its x^2 - (x-1)*(x+1)
(x-1)*(x+1) = x^2 -1

=> x^2 - (x^2-1) i.e. 1

So answer is 1

Answer 3

1 ALWAYS works!
(n*n) - (((n-1)*(n+1)=1