Question

-b/2a等于2 4ac-b的平方/4a等于 1 a＋b＋c等于 0 各是多少

Answer 1

这道题和一元二次函数联系起来,

其一般式：

y = ax² + bx + c; (1)

一元二次函数的顶点坐标是:

x = -b/2a = 2 ; y = (4ac-b²)/4a = 1

所以列出一元二次函数的顶点式：

y = a(x + b/2a)² + (4ac-b²)/4a

y = a(x - 2)² + 1 (2)

根据(1):

x = 1时：

y = a + b + c

而 a + b + c = 0,

所以 y = 0;

根据(2):

x = 1时：

y = a + 1

y = 0;

a + 1 = 0;

a = -1;

-b/2a = 2;

b = 4;

a + b + c = 0

c = -3

a = -1;

b = 4;

c = -3;