Question

If x= 1 / 2 - √3 , find the value of x³ - 2x² - 7x +5
A. 1
B. 0
C. 2+√3
D. 3

Please give a proper solution and ans it fast

Answer 1

x=1/(2-√3)=1/(2-√3)×(2+√3)/(2+√3)
x=2+√3

=x^3-2x^2-7x+5

=x(x^2-2x-7)+5

=(2+√3){(2+√3)^2-2(2+√3)-7}+5

=(2+√3){4+3+4√3-4-2√3-7}+5

=(2+√3){2√3-4}+5

=4√3-8+6-4√3+5

=3

Hence value of x^3-2x^2-7x+5 ,when x=1/(2-√3) = 3.