This depends on three things;
The type of defect,
if it was a manufacturers defect (it just stopped working)
and not abuse,
the it probably will be covered.
The type of coverage the extended warranty covers;
does it cover all components or just the main board and hard drive (I`ve seen these types of deceptive "extended warranties" before),
some warranties specifically don`t cover the power adapter,
battery and LCD screen.
You need to read your warranties fine print.
The time line of coverage from the extended warranty.
Some extended warranties only kick in after the original manufacturers warranty has run out.
If that is the case with your warranty,
and you are still within the manufacturers warranty,
they will refer you to the manufacturer (Apple).
In any of these cases,
you need to read up on what your warranties cover and what they won`t.