（x-2)(x-m)=（p-2)(p-m) x^2-xm-2x+2m = p^2-pm-2p+2m x^2-xm-2x = p^2-pm-2p x^2-xm-2x-p^2+pm+2p=0 x^2-p^2-x(m+2)+p(m+2)=0 (x+p)(x-p)-(m+2)(x-p)=0 (x-p)(x+p-m-2)=0 x1=p,x2=m+2-p
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