Hello,
Pytagorean's triples are like x²+y²=z² with x,y,z integers.
Let's suppose x=p²-q², y=2pq
then
x²=(p²-q²)²=p^4-2p²q²+q^4
y²=4p²q²
so
x²+y²=p^4+q^4-2p²q²+4p²q²=p^4+2p²q²+q^4=(p²+q²)²
Thus (p²-q²,2pq,p²+q²) is a Pythagorean's triple.
Examples:
p=2 and q=1 ==>p²-q²=4-1=3, 2pq=2*2*1=4,p²+q²=2²+1²=5 (3,4,5)
p=4 and q=3 ==>p²-q²=4²-3²=16-9=7, 2pq=2*4*3=24, p²+q²=4²+3²=16+9=25 (7,24,25)
...