Question

一元二次方程ax一元二次方程ax^2+bx+c=0(a≠0)的两根为x1和x2

Answer 1

x1+x2=-b/a

x1x2=c/a

1、

︱x1-x2｜

=√（x1-x2)²

=√(x1+x2)²-4x1x2

=√b²/a²-4c/a

=√(b²-4ac/a²)

（x1+x2）/2

=-b/2a

2、

x1^3+x2^3

=(x1+x2)(x1²+-x1x2+x2²)

=(x1+x2)((x1+x2)²-3x1x2)

=（-b/a）(（-b/a)²-3c/a)

=(-b/a)(b²-3ac/a²)

=(3abc-b³)/a³