Question

If x= 1÷2-√3,then what is the value of xcube + 2xsquare- 7x-5​

Answer 1

ANSWER:

x = 1/2-√3

rationalizing the value

x= (1/2-√3)*(2+√3)/(2+√3)

x= [(2+√3)*1]/[(2)^2-(√3)^2]

x=2+√3      -----------------i

now the equation xcube + 2xsquare - 7x -5

put the value of x from equ. (i)

(2+√3)^3+2(2+√3)^2-7(2+√3)-5

8+√27+3(4)√3+3(2)(3)+2[4+3+4√3]+14+7√3-5

8+3√3+12√3+18+14+8√3+14+7√3-5

8+18+14+14-5+3√3+12√3+8√3+7√3

49+30√3