Question 194045
( 4a -5 ) (4a^2 +a -4 )
, 
,,,,,,,16a^3  +  4a^2  -  16a
,,,,,,,,,,,,,,,,,- 20 a^2   -   5a  +  20
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,,,,,,,,16a^3  - 16a^2    -21a   +20  

,
check
let  x=1  in  both  original  and  answer,  both  gave  (-1),,,ok