What is this called? How do I get rid of it?

Question

Grass is two years old and is being cut regularly, have taken out some of these weeds but seem to be returning and expanding. Thanks

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Answer 1

This looks to be Creeping Buttercup.
This article will help you with control.
https://www.gardeningknowhow.com/plant-problems/weeds/how-to-kill-buttercup-weeds.htm