>>251求める放物線をｙ＝a(ｘ−ｐ)^2とおく。(a≠0)
3＝a(2−ｐ)^2
12=a(−1−ｐ)^2
∴(a,p)＝(3,1),(1/3,5)

ｙ＝３(ｘ−1)^2
ｙ＝(1/3)*(ｘ−5)^2