y=x2-mx+m2-n的頂點在直線y=2x+1上,m-n=-2
y=x2-mx+m2-n=(x-m/2)^2+3m^2/4-n
頂點為（m/2,3m^2/4-n）
代入直線y=2x+1
=>3m^2/4-n=2*m/2+1
=>3m^2-4n=4m+4
=>3m^2-4m-4n-4=0 又m-n=-2 =>n=m-2
=>3m^2-8m+4=0
(3m-2)(m-2)=0
=>m=2/3,n=-4/3
或m=2,n=0
所以拋物線方程為
y=x2-mx+m2-n=x2-2x/3-1/3
或
y=x2-mx+m2-n=x2-2x+2