Question

已知二次函数y=1/3(x-1)^2-3,回答当x取何值时 (1)y＞0?(2)y=0?(3)y随着x的增大而减小?

Answer 1

1/3(x-1)^2-3=0

(x-1)^2=9

x-1=±3

x=4或x=-2

故1)x4时y>0

2)x=4或x=-2时y=0

3)x