Question

If (x+1/x) =9 find the value of x³+1/x³

Answer 1

Step-by-step explanation:

x+1/x=9

squaring both side

x2+1/x2+2×1/x2×x2=(9)2

x2+1/x2=81-2=79

Multiply first and second equation

(x+1/x)(1/x2+x2)=79

x3+x+1/x+1/x3=79

x3+1/x3+(x+1/x)=79

x3+1/x3+9=79

x3+1/x3=79-9=70