Cannot curve edges when combining shapes on Adobe Illustrator iPad

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I appoligize in advance for my rudimentary explanation. I am trying to create a pattern for a card holder. I have combined a rectangle and an elipse in order to create a divet after hitting "minus front". Unfortunately, I cannot curve the edges of the divet. I can do it for the original corners of the rectangle, but not the ones created from combining the shapes. Any advice is appreciated. 

 

[Monika Gause]

That is a compound shape. You have to first expand it. You can do that cia the pathfinder panel as well.