Equation numbering

[Rem]

Hi,

In report style, how can I have equations to be numbered by incorporating
the "section numbers" in?
I can not show the section numbers in the section titles.

Say I have the section title for section 2 as:

PRELEMINARIES

my first equation should be numbered as:

y(t)=a.x(t)            (2.1)

Any idea?

Regards,

Remzi