Question

已知二次函数y=ax的平方＋bx＋c的y与x的部分对应值如又表

Answer 1

x = 0, y = c = 1
x = -1, y = a - b + c = a - b + 1 = -3, a - b = -4
x = 1, y = a + b + c = a + b + 1 = 3, a + b = 2
相加，a = -1
b = 3
a < 0, 开口向下
其它看不清楚.