Question

解不等式x²一x一5<0？

Answer 1

x²-x-5 = 0， x = （1±√21)/2
x²-x-5 < 0 解集是, (1-√21)/2 < x < (1+√21)/2

Answer 2

(x-3)(x+2)<0
解得：-2<x<3

Answer 3

x^2-x-5<0
(x-1/2)^2 < 21/4
-√21/2<x-1/2<√21/2
(1-√21)/2<x<(1+√21)/2