Let's use x for variables with the meaning of x=5, x=-4, and x=1

Now, let's express it in formula:

(x-5)(x+4)(x-1)=0

(x^{2}-5x+4x-20)(x-1)=0

(x^{2}-x-20)(x-1)=0

x^{3}-x^{2}-20x-x^{2}+x+20=0

x^{3}-2x^{2}-19x+20=0