4x^3 -11x^2 + 2x + 3
Test whether 3/4 is a root
3/4 [ 4 -11 2 3 ]
3 -6 -3
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4 -8 -4 0
It is a root
The remaining polynomial is
4x^2 - 8x - 4 = 0
x^2 -2x - 1 =0
x^2 -2x = 1
x^2 -2x +1 =1 + 1
(x -1)^2 = 2 take both roots
x -1 =sqrt 2 x - 1 = -sqrt 2
x = 1 + sqrt 2 x = 1 - sqrt 2
These are the other two roots