Question

Show that (X +2)is a factor of x³-4x²-2x+20

Answer 1

Here , 

x+2 =0

then x=-2

Let's put f(x) =-2 in given equation

x³-4x²-2x+20

= f(-3)= (-2)³-4*(-2)² -2*(-2) +20

             -8-16+4+20

              -24+24

                  =0

hence ,x+2 is a factor of given polynomial f(x).

         Thank you