# Math Help - Algebra thing AS Level

1. ## Algebra thing AS Level

hi.

how do i prove using the difference of 2 squares that :

when you take a prime number bigger than 3, square it and then minus 1 the answer is always a multiple of 24

please helllllp

2. Hello,
Originally Posted by Megiarno
hi.

how do i prove using the difference of 2 squares that :

when you take a prime number bigger than 3, square it and then minus 1 the answer is always a multiple of 24

please helllllp
Let p be this prime number.

"square it and then minus 1 the answer" : p²-1
Use the difference of squares formula.

Then, remember that a prime number can only be in the form $6k \pm 1$, with $k \text{ an integer } \ge 1$ (if it was $\pm$ 0, 2, 3, 4, p wouldn't be prime)

3. ## hm

i know that the d.o.t.s is now (p+1)(p-1) but where do i go from there?