Explicație pas cu pas:
x³+5x²-4x-20=x²(x+5)-4(x+5)=(x+5)(x^2-4)=(x+5)(x-2)(x+2)
x³+10x²+31x+30=x³+5x^2+5x^2+25x+6x+30=
x^2(x+5)+5x(x+5)+6(x+5)=(x+5)(x^2+5x+6)=(x+5)(x+2)(x+3)
F(x)=(x+5)(x+2)(x-2)/(x+5)(x+3)(x+2)=(x-2)/(x+3)
F(x)€Z <=> x+3|x-2
x+3|x-2
x+3|x+3
=> x+3|x+3-x+3=>x+3|5 =>x+3€D5 in Z =>
x+3€{-5,-1,1,5} => x€{-8,-4,-2,2} => A={-8,-4,+-2}
