The polynomial p(x) is, p(x)= x3-5x2-8x+48.Use the Factor Theorem to show that (x + 3)is a factor of p(X)

First of all it is using the factor theorem. 

so need to use that to show it is a factor 

We do this by P of (-3) should = 0 

So substitute x with -3 

 p(-3)= (-3)3 - 5 (-3)2- (-3)8 + 48

= 0 

-27-45+24+48=0