SSIS expression: get previous date in yyyy-mm-dd

Hi, 

For the syntax below, i got 2018-09-17

(DT_STR,4,1252)DATEPART( "yyyy" , getdate() ) +  "-" +
RIGHT("0" + (DT_STR,4,1252)DATEPART( "mm" , getdate() ), 2) +  "-" +
RIGHT("0" + (DT_STR,4,1252)DATEPART( "dd" , getdate() ), 2)

get previous date, I have  -1 but got error, not sure why?

(DT_STR,4,1252)DATEPART( "yyyy" , getdate() ) +  "-" +
RIGHT("0" + (DT_STR,4,1252)DATEPART( "mm" , getdate() ), 2) +  "-" +
RIGHT("0" + (DT_STR,4,1252)DATEPART( "dd" , getdate()-1 ), 2)

Thanks