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Prove that any number having any power can be expressed as difference of two squares & also prove that the numbers of the form 4t+2 canot be expressed as difference of two squares.

2006-10-13 22:39:56 · 5 answers · asked by rajesh bhowmick 2 in Science & Mathematics Mathematics

like 3^(3)= 14^(2)-13^(2)

2006-10-13 22:53:47 · update #1

5 answers

both are easy

any number having any power > 1(for power 1 for the form 4t+2) is not possible

it is odd

say 2n+1 = (n+1)^2 - n^2

it is even then it is divisible by 4^n . if is not divisible by 4^n then it is 4^n. 2 and mth root cannot be taken.
let highest power of 2 is 2^2n because it cannot be odd

so 2^n.odd

odd can be subtract of 2 perferct squares.

so multiply both by 2^n so even powe can be perfect of 2 squares

b)
the number is of the form 4n+2

difference of 2 squares say a and b

a can be 2n or (2n+1) =>a^2 = 4n^2 or 4n^2+4n+1
b can be 2m or 2m+1 =>b^2 = 4m^2 or 4m^2+4m+2


a^2 mod 4 = 0 or 1
b^2 mod 4 = 0 or 1
a^2 -b^2 mod 4 = 0-0 or 1-0 or 0-1 or 1-1
= 0 or 1 or -1 or 0

so it cannot be 2
so it is not of the form 4t+2

2006-10-13 23:00:25 · answer #1 · answered by Mein Hoon Na 7 · 0 0

For second question:
4t + 2 = ?
Let t = -0∙5
4t + 2 = ?
4(-0∙5) + 2 =
-2 + 2 = 0
Can zero be expressed as the difference of two squares ?

2006-10-14 06:04:14 · answer #2 · answered by Brenmore 5 · 0 0

is the ansewr a number or a number with a power or what. That confused me. My streanght is apperantly a zero.

2006-10-14 05:42:07 · answer #3 · answered by granite 1 · 0 0

I expected a question on keep fit!.........pass!

2006-10-14 05:44:23 · answer #4 · answered by expatriot1000 4 · 1 0

No, I wont help with your homework ;-)

2006-10-14 05:50:21 · answer #5 · answered by Anonymous · 0 1

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