Question

x+1/x=9 then evaluate x3+1/x3

Answer 1

Answer:

$x^3+\frac{1}{x^3}=702$

Step-by-step explanation:

$x+\frac{1}{x}=9\\Squaring\;on \;both\;sides\\(x+\frac{1}{x})^2=81\\x^2+\frac{1}{x^2}+2=81\\x^2+\frac{1}{x^2}=79\\WKT\\x^3+\frac{1}{x^3}=(x+\frac{1}{x})(x^2+\frac{1}{x^2}-1)\\x^3+\frac{1}{x^3}=9*78\\x^3+\frac{1}{x^3}=702$

Hope It Helps