什么方程?是抛物线吗?
y=ax^2+bx+c,顶点坐标为(-b/2a,(4ac-b^2)/4a)在原点上
-b/2a=0,b=0
(4ac-b^2)/4a=0,c=0
把(2,5)点代入y=ax^2得a=5/4
y=(5/4)x^2