​ What are the zeros of the polynomial function?

x^4  - 2x^3  - 103x^2   + 200x  + 300

Write  -103x^2   as  -3x^2   -  100x^2

So we have

x^4 - 2x^3  - 3x^2  -  100x^2 + 200x +  300

x^2 (x^2 - 2x - 3) - 100 (x^2 - 2x - 3)        take out the common factor

(x^2 - 2x - 3)  (x^2 - 100)

(x - 3) ( x + 1) (x + 10) (x - 10)

Note that the zeroes are  x =  3 , -1, -10, 10