# Legendre symbol

• May 15th 2011, 07:29 AM
joi
Legendre symbol
Can't figure out why -(7/3)=-(4/3) Anyone can make it simple for me.
• May 15th 2011, 07:42 AM
tonio
Quote:

Originally Posted by joi
Can't figure out why -(7/3)=-(4/3) Anyone can make it simple for me.

$\binom{7}{3}=\binom{1}{3}=1\,,\,\,\binom{4}{3}= \binom{1}{3}=1$ , when taking $4,7=\!\!\pmod 3$

Tonio
• May 15th 2011, 09:08 AM
joi
Thanks Tonio. Can somebody evaluate (7/79). I keep getting (-1). The answer in the back of the book is 1. Obviously I am making a mistake.
• May 15th 2011, 10:39 AM
AmateurStudent
I get (7/79) = -(2/7) = -(1/7) = -1
Maybe the answer in the back of the book is wrong?
• May 16th 2011, 07:55 PM
Drexel28
Quote:

Originally Posted by AmateurStudent
I get (7/79) = -(2/7) = -(1/7) = -1
Maybe the answer in the back of the book is wrong?

I agree