How to deal with this ?

My aunt ( a very old person) has a house in California...

She has had the home over 18 years now.

There are 2 trees whose roots are lifting the concrete pretty high.

She has been told that she needs to get rid of the trees and that there
is a "special something" that needs to be applied on the cut trunk
....or something...

Would anyone know what needs to be applied to the cut trunk to
permanently kill the trees?

Can anyone suggest a better way to get rid of these 2 trees ?

What do people normally do when the roots of a tree lift the concrete ?
How does one rectify such a situation ?

Does one have to remove all the roots or can one just kill the tree
from the trunk ?

Thank you all in advance for your input,
Rita