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

–1 vote
1,664 views
Calculate (123456789 X 123456789) - (123456788 X 123456790) without calculator?
posted Sep 28, 2015 by anonymous

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3 Answers

+1 vote

Solution = 1

Let a = 123456789

Then

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

answer Oct 3, 2015 by Forrest Dale
0 votes

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 Oct 1, 2015 by Salil Agrawal
0 votes

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

answer Nov 14, 2015 by anonymous
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