「頂点A」と「通る点B」で決まる
２次関数の式を求めてみよう．

A = (2, 5)
B = (-1, -4)
aa: (y(B) - y(A)) / (x(B) - x(A))^(2)
f = Simplify((aa * (x - x(A))^(2)) + y(A))
bb: ((-2 * aa) * x(A))
cc: ((aa * x(A)) * x(A)) + y(A)
g(x) = (aa * x^(2)) + (bb * x) + cc
texta = If(aa ≟ 0, " ", If[aa ≟ 1, "x^2", If[aa ≟ -1, "-x^2", Text[aa] + "x^2"]])
textb = If(bb ≟ 0, " ", If[bb ≟ 1, "+x", If[bb ≟ -1, "-x", If[bb > 0, "+" + (Text[bb]) + "x", Text[bb] + "x"]]])
textc = If(cc ≟ 0, " ", If[cc > 0, "+" + (Text[cc]), Text[cc]])
text1: "f(x)=" + (LaTeX[texta]) + "" + (LaTeX[textb]) + "" + (LaTeX[textc]) + ""