Question

x+1/x=7 x*x*x+1/x*x*x=????☺

Answer 1

$x+ \frac{1}{x} = 7$
cubing on both sides
$(x+ \frac{1}{x})^3 = 7^3$
$x^3 + 3.x. \frac{1}{x}[x+ \frac{1}{x}] + \frac{1}{x^3} = 343$
$x^3 + 3[7] + \frac{1}{x^3} = 343$
$x^3 + 21 + \frac{1}{x^3} = 343$
$x^3 + \frac{1}{x^3} = 322$