Question

solve this plz urgent need

Answer 1

Answer:

x³+1/x³=18

Step-by-step explanation:

x=(3+√5)/2

1/x=2/(3+√5)*(3-√5)/(3-√5)

=2*(3-√5)/(3+√5)(3-√5)

=(6-2√5)/9-5

=6/4-2√5/4

=3/2-√5/2

x+1/x=(3+√5)/2+3/2-√5/2

=3/2+√5/2+3/2-√5/2

=3/2+3/2

=6/2=3

x+1/x=3

Now x³+1/x³=(x+1/x) (x²+1/x²-x*1/x)

=3*(x²+1/x²+2x*1/x-3x*1/x)

=3*[ (x+1/x)²-3]

=3*(3²-3)

=3*(9-3)=3*6

=18