Respuesta :

Answer:

Step-by-step explanation:

i think you want to know if x-3 is a factor.

x-3=0

x=3

3 ) 2  -3  -20  -21

  |       6   9    -33

  |----------------------

     2   3  -11  |-54

remainder is not zero,it is -54

so x-3 is not a factor of 2x^4-3x²-20x-21