Multiplying two polynomials without using conv() function

How can I multiply two polynomials without usiing conv() function?

%two polynomials
a = [13,-13]    %a = 13x - 13
b = [-13,9,8]   %b = -13x^2 + 9x + 8

I am trying to return the result of the mutiplication like this

m = [-169, 286, -117, -104]

Answer 1

[Ameer Hamza]

"without using conv() function"

syms s

a = [13,-13]    %a = 13x - 13
b = [-13,9,8]   %b = -13x^2 + 9x + 8

ab = sym2poly(poly2sym(a, s)*poly2sym(b, s))

Result

>> ab
ab =
  -169   286   -13  -104

Answer 2

[Saleh AlSenaidi]

If you don't have symbolic toolbox, you can use this code

a = [13,-13];    %a = 13x - 13
b = [-13,9,8];   %b = -13x^2 + 9x + 8
roots_a =roots(a);
roots_b =roots(b);
ab      =a(1,1)*b(1,1)*poly([roots_a.',roots_b.'])

Note: X.' is the non-conjugate transpose of X.

Resut

>> ab
ab =
          -169         286         -13        -104