How can I solve the equation : 120=x(x-1)(x-2)(x-3)

The equation to be solved is :
120=x(x-1)(x-2)(x-3)

120 = x(x - 1)(x - 2)(x -
3)

=> 120 = x^4 - 6*x^3 + 11*x^2 -
6*x

=> x^4 - 6*x^3 + 11*x^2 - 6*x - 120 =
0

=> x^4 - 5x^3 - x^3 + 5x^2 + 6x^2 - 30x + 24x -120
= 0

=> x^3(x - 5) - x^2(x - 5) + 6x(x - 5) + 24(x -
5) = 0

=> (x - 5)(x^3 - x^2 + 6x + 24) =
0

=> (x - 5)(x^3 + 2x^2 - 3x^2 - 6x + 12x + 24) =
0

=> (x - 5)(x^2(x + 2) - 3x(x + 2) + 12(x + 2)) =
0

=> (x - 5)(x + 2)(x^2 - 3x + 12) =
0

This gives the roots x1 = 5 and x2 =
-2

From x^2 - 3x + 12 = 0, we get the
roots

x3 = 3/2 + sqrt (9 -
48)/2

=> 3/2 + i*sqrt
39/2

x4 = 3/2 - i*sqrt
39/2

The solutions of the given equation are
(5, -2, 3/2 + i*sqrt 39/2, 3/2 - i*sqrt 39/2)