We take the derivative of x^3 -6x^2 + 4x -3 which is
3x^2 -12x +4 = 0
Then we have to calculate the equation's value when y = 0 which in this case occurs when x = 5.3579 (the equation's only real root).
3*5.3579 * 5.3579 -12*5.3579 +4 = 25.82647723
which rounds to 25.826
Explanation: