Not another Perfect Square Problem

Product of any 4 consecutive integers is always 1 less than a perfect square.

5 Answers

341
Hari Shankar ·

Is everyone on a holiday or what? That's the only explanation for this one to go unanswered.

62
Lokesh Verma ·

lol.. i guess ;)

atleast the xi class guys should be trying this one ;)

49
Subhomoy Bakshi ·

n(n+1)(n+2)(n+3)

=(n2+3n)(n2+3n+2)

=n4+6n3+9n2+2n2+6n

=n4+6n3+11n2+6n+1-1

=(n2)2 + (3n)2 + (1)2 + 2.(n2).(1) + 2.(3n).(1) + 2.(n2).(3n) - 1

=(n2 + 3n +1)2 - 1

=k2 - 1

thus, n(n+1)(n+2)(n+3) is 1 less than a perfect square!! :D

62
Lokesh Verma ·

n(n+1)(n+2)(n+3)

=(n2+3n)(n2+3n+2)

you made it worse from here

t(t+2) = t2+2t+1-1 = (t+1)2-1

49
Subhomoy Bakshi ·

hehe yea....

didi it in that way...

and just b4 completing just forgot why i had grouped it :P

stupid me! :P

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