x^3 - 4x^2 - 5x + 20 = 0;
(x^3 - 4x^2) - (5x - 20) = 0;
x^2(x - 4) - 5(x - 4) = 0;
(x - 4)(x^2 - 5) = 0;
(x - 4)(x - √5)(x + √5) = 0;
1) x - 4 = 0;
x = 4;
2) x - √5 = 0;
x = √5;
3) x + √5 = 0;
x = -√5.
x^3 - 4x^2 - 5x + 20 = 0;
(x^3 - 4x^2) - (5x - 20) = 0;
x^2(x - 4) - 5(x - 4) = 0;
(x - 4)(x^2 - 5) = 0;
(x - 4)(x - √5)(x + √5) = 0;
1) x - 4 = 0;
x = 4;
2) x - √5 = 0;
x = √5;
3) x + √5 = 0;
x = -√5.