Question

Find the value of x+1/x=3, then find x^3+1/x^3​

Answer 1

x+1x=3x+1x=3

(x+1x)3=33(x+1x)3=33

x3+3.x2.1x+3.x.1x2+1x3=27x3+3.x2.1x+3.x.1x2+1x3=27

(x3+1x3)+3.x2.1x+3.x.1x2=27(x3+1x3)+3.x2.1x+3.x.1x2=27

x3+1x3+(3x+3x)=27x3+1x3+(3x+3x)=27

x3+1x3+3(x+1x)=27x3+1x3+3(x+1x)=27

x3+1x3+3×3=27x3+1x3+3×3=27

the answer is 18