(х-3) : x^2-6x+9/x+3 при х=-21
(х-3) : ((x²-6x+9)/(x+3)) = (х-3) : ((x-3)²/(x+3)) = (х-3) * ((x+3)/(x-3)²) =
= (х+3)/(x-3)
при х= - 21 (21+3)/( 21-3) = 24/18 = 4 /3 = 1. 1/3