2 x 2 − 3 y 2 = 2 0 1 4
How many integer solution(s) are possible for the equation above?
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Nice solution! :)
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What happened?
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Nothing,I just wanted you to see my solution.:)
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@Adarsh Kumar – It's good!!
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@Anik Mandal – Thanx a lot!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
2 x 2 − 3 y 2 = 2 0 1 4 2 − 3 y 2 = 1 0 0 7 − x 2 y 2 = ( 1 0 0 7 − x 2 ) ( 3 − 2 ) ∴ 3 ( x 2 − 1 0 0 7 ) ( 2 ) = y 2 2 ≡ 2 ( m o d 3 ) ∴ x 2 ≡ 2 ( m o d 3 ) B u t t h i s i s i m p o s s i b l e . x 2 c a n o n l y b e i d e n t i c a l t o 0 o r 1 . T h e r e f o r e , t h e r e a r e n o s u c h v a l u e s .
or, if code is not displaying, https://drive.google.com/file/d/0B42CxY5sovrLdWtrOWhOWWpleDQ/view?usp=sharing
Could you explain the last 2 steps .
The one in which you used Mod
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The equation given to us is 2 x 2 − 3 y 2 = 2 0 1 4 . Now, 2 x 2 =even and 2 0 1 4 = even.Thus, 3 y 2 = even ⟹ y 2 = even ⟹ y = even.Let us say that x = ( 2 b + 1 ) , y = 2 a . Plugging that into the equation given,we get : 2 ( 2 b + 1 ) 2 − 3 ( 4 a 2 ) = 2 0 1 4 . Simplifying gives 8 b 2 + 2 + 8 b − 1 2 a 2 = 2 0 1 4 . This gives, 8 b ( b − 1 ) − 1 2 a 2 = 2 0 1 2 ⟹ 2 b ( b − 1 ) − 3 a 2 = 5 0 3 (dividing by 4).This gives that 3 a 2 = odd. ⟹ a = odd.Taking a = 2 c + 1 gives 2 b 2 + 2 b − 1 2 c 2 − 3 − 1 2 c = 5 0 3 . ⟹ 2 ( b 2 + b − 6 c 2 − 6 c = 5 0 6 . This simplifies to b ( b + 1 ) − 6 c ( c + 1 ) = 2 5 3 . But this can't happen as b ( b + 1 ) = even.Because the product of two consecutive numbers is always even.Obviously, 6 c ( c + 1 ) = even.But even-even=even.Thus,the answer is 0 .