go at vs mix it up

go at

verb
  • To initiate an attack on or an argument with. 

  • Used other than figuratively or idiomatically: see go, at. 

  • To try to solve a problem a specific way; to undertake a task. 

mix it up

verb
  • To compete vigorously, to quarrel, or to fight physically. 

  • To create one or more variations of the usual way in which something is done. 

  • To engage with people, relate to people. 

How often have the words go at and mix it up occurred in a corpus of books? (source: Google Ngram Viewer )