(x-p)的平方=x的平方+x+1/4
(x-p)的平方=(x+1/2)的平方
(x-p)的平方-(x+1/2)的平方=0
(x-p+x+1/2)(x-p-x-1/2)=0
(2x-p+1/2)(p+1/2)=0
p=-1/2
(1-2p)^2=(1-2*(-1/2))^2=2^2=4