x²-4x-p²+2p+2=0
x²-4x+4=p²-2p+2
(x-2)²=p²-2p+2
x=2+√(p²-2p+2)或x=2-√(p²-2p+2)
q=2+√(p²-2p+2)或q=2-√(p²-2p+2)