Question
I live in zone 5 near the great lakes.

This year a plant took over a large part of my yard that is in shade.

The leaf is in the shape of a trapazoid and is about 4 inches in length.  There are two leafs on each flower which is a star shaped, yellow flower about an inch or so.  Also, the leaf is a dull green  with dark markings on it.

The area that they are growing in has enough of them to resemble a ground cover.

I hope you can help with this so I decide what to do about it.  Thanks

Answer
Is this what you have http://www.ct-botanical-society.org/galleries/erythroniumamer.html ?  If it is, it probably has been there all along and this is the first time you noticed it.

Dogtooth Violet, also known as Trout Lily, is a native plant.  It grows from tiny tubers that are 3" below the surface.  It will go dormant soon after blooming and you won't see it again until next spring.  It will not interfere with anything else you might want to plant in that location.

I would just leave it alone if I were you.  If you plant another groundcover such as Pachysandra on top of it, you will lose it.  I have planted hostas in the bed where it grows, and the two coexist happily.